Multimedia and Animation, Essays (university) of Computer Science

Download Multimedia and Animation and more Essays (university) Computer Science in PDF only on Docsity! & STATE OPEN UNIVERSITY hGRNGOTRI, MYSORE; 570 006 MODULE: 1-4 2 MSIT-121D (Elective 2): Multimedia and Animation 5 PREFACE Multimedia and animation is emerging trend in the field of information technology. Multimedia and animation has gained tremendous attention from various industries. A lot of new technologies in multimedia and animation are developing day by day. To cope up with industry requirement this course has been designed in such a way that it balances theoretical aspects as well as practical issues. The objective of this course is to understand the principles and applications of Multimedia and Animation; to acquire skills to use Multimedia and Animation applications; to integrate and synchronize the Multimedia and Animation techniques for new application problems. The overall structure of the material is divided into four main modules. Each module consists of four units. In summary Module 1 gives precise introduction to field of Multimedia, which covers Definition and nature of multimedia - different media elements, types of data, classification of multimedia, Benefits of multimedia, multimedia works in learning Multimedia-, media elements. Learning and multimedia, Benefits of multimedia in learning, Designing multimedia applications, Multimedia design: Multimedia Digital Imaging. Module 2 discusses about multimedia graphic formats, 3D formats, different types of multimedia tools for editing audio, video and text data. It also covers topics such as 2D geometric transformation and the viewing pipeline. In module 3, we introduce animation. The very first unit gives definition of animation, the history of animation and line art methods in animation. In the later part we discussed different between file and animation, principles of animation and basic animation techniques. In the last two units of module three we bring out some advance concepts in animation such techniques corresponds to bitmapped and shape elements, recording animation, Classification of Animation, difference between conventional method of animation and digital animation, types of animation. In the final module, Animation and file formats, Hardware and software requirements, Difference between 2D and 3D animation - film, cartoon movie, animation and broadcasting, authoring tool, presentations, applications, interaction, 2D and 3D animations- projects simple animations, Animation files and internet, Movie types and its uses in supportability for the web are discussed. In the reference section we have given links for further reading for the students to get addition knowledge on multimedia and animation. Wish you happy reading !!! 6 MODULE-1 UNIT-1 Introduction to Multimedia Structure 1.0 Objectives 1.1 Introduction 1.2 Definition of Multimedia 1.3 Media elements 1.4 Benefits of Multimedia 1.5 Multimedia in Learning 1.6 Designing multimedia applications 1.7 Digital imaging 1.8 Summary 1.9 Keywords 1.10 Exercise 1.11 References 1.0 Learning objectives After studying this unit, you will be able to,  define multimedia,  mention applications of multimedia.  describes the elements & classes of multimedia  state benefits of multimedia.  Explain multimedia in learning,  design of multimedia 1.1 Introduction of multimedia Multimedia systems are becoming an integral part of our heterogeneous computing and communication environment. We have seen an explosive growth of multimedia computing, communication, and applications over the last decade. The World Wide Web, conferencing, digital entertainment, and other widely used applications are using not only text and images but 7 also video, audio, and other continuous media. In the future, all computers and networks will include multimedia devices. They will also require corresponding processing and communication support to provide appropriate services for multimedia applications in a seamless and often also ubiquitous way. Multimedia is probably one of the most overused terms of the 90s. The field is at the crossroads of several major industries: computing, telecommunications, publishing, consumer audio-video electronics, and television/movie/broadcasting. Multimedia only brings new industrial players to the game, but adds a new dimension to the potential market. 1.2The term “Multimedia” The word multimedia is composed of two parts: the prefix Multi and the root Media. The prefix Multi does not pose any difficulty; it comes from the latin word multus, which means ‗numerous‖ or ―many‖. The root media has a more complicated story. Media is plural form of the latin word medium. Media is noun and means ―middle, center‖. 1.2 The definition of multimedia ―Multimedia is the integration of multiple forms of media. It includes text, audio, animations, and video and so on.‖ Medium is ―a means to distribute and represent information‖. Media are, for example, text, graphics, picture, voice, sound and music. 1.2.1 Classification of media Each medium defines,  Representation values - determine the information representation of different media – Continuous representation values (e.g. electro-magnetic waves) – Discrete representation values(e.g. text characters in digital form) 10  Audio Messages  Voice messages refer to a message that could be sent to a destination using voice media.  Video Messages  Video messages refer to a message that could be sent to a destination using video transmission media.  Full motion stored and Live Video (FMV)  Full motion video started out as a very useful idea for online training and maintenance manual.  The evolutionary step of FMV is video conferencing.  Holographic images  Holographic images extend the concept of virtual reality by allowing the user to get ―inside‖ a part such as operations from the outside.  Fractals  This technology is based on synthesizing and storing algorithms that describe the information. 1.4 Benefits of multimedia Multimedia is widely used in applications like,  Teleconferencing  VoIP(Voice over IP)  PC –to- PC.  PC-to-Telephone.  Audio, Video and Multimedia messages  Voice mail.  Multimedia mail.  Geographical Information System.  Image processing and image recognition.  Video Conferencing.  Universal Applications  Education. 11  Science and Technology.  Medicine.  Business  Advertisements.  Training materials.  Presentations.  Customer support services.  Entertainment  Interactive Games.  Animation.  Enabling Technology  Accessibility to web based materials  Teaching-learning for disabled children and adults.  Fine Arts and Humanities  Museum tours.  Art exhibitions.  Presentations of literature. 1.5 Multimedia in learning In many ways, ours has been a multimedia society for decades. A variety of media - print material, film strips, and visual aids - have been used in the classroom for years. Conferences and seminars have made effective use of music, lights, slide projectors and videotapes. And ubiquitous televisions have shaped a new multimedia generation. What differentiates multimedia as the buzzword of the nineties, however, is the partnership potential of multiple media and computer technologies. Computers can now present data, text, sound, graphics, and limited motion video on the desktop. Computer based multimedia skill and knowledge applications offer benefits and value difficult to equal in non-technology implementations. 12 The use of multimedia in learning offers many advantages: 1. Enhancement of Text Only Messages: Multimedia enhances text only presentations by adding interesting sounds and compelling visuals. 2. Improves over Traditional Audio-Video Presentations: Audiences are more attentive to multimedia messages than traditional presentations done with slides or overhead transparencies. 3. Gains and Holds Attention: People are more interested in multimedia messages which combine the elements of text, audio, graphics and video. Communication research has shown that the combination of communication mode (aural and visual) offers greater understanding and retention of information. 4. Good for "computer-phobic": Those who are intimidated by computer keyboards and complex instructions are more comfortable with pressing buttons with a mouse or on a screen. 5. Multimedia is Entertaining as well as Educational: Relative industries Creative industries use multimedia for a variety of purposes ranging from fine arts, to entertainment, to commercial art, to journalism, to media and software services provided for any of the industries listed below. An individual multimedia designer may cover the spectrum throughout their career. Request for their skills range from technical, to analytical, to creative. Commercial uses Much of the electronic old and new media used by commercial artists is multimedia. Exciting presentations are used to grab and keep attention in advertising. Business to business, and interoffice communications are often developed by creative services firms for advanced multimedia presentations beyond simple slide shows to sell ideas or liven-up training. Commercial multimedia developers may be hired to design for governmental services and nonprofit services applications as well. 15 The rapid evolution and spread of GUIs has made it possible to implement multimedia applications widely accessible to desktop users in an office environment. In the subsequent sections, we will look at these applications and then present a view of generic multimedia applications. 1.6.1 Document Imaging The first major step toward multimedia was originated in document image management systems. Organizations such as insurance agencies, law offices, country and state governments, including the department of defense, manage large volume documents. In fact, the Department of Defense (DOD) is among the early adopters of document image technology for applications ranging from military personal records to maintenance manuals and high speed printing systems. The source of interest in imaging is due to its workflow management and contribution to productivity. Document imaging makes it possible to store, retrieve, and manipulate very large volume of drawings, documents, and other graphical representation of data. Imaging also provides important benefits in terms of electronic data interchange, such as in the case of sending large volume of engineering data about complex systems in electronic form rather than on paper. Imaging is already being used for a variety of applications. An application such as medical claims processing not only speeds payment to healthcare facilities, but cuts costs of reentering information from claim forms into a computer database. OCR systems now automatically handle the task of data entry of key fields. 1.6.2 Image Processing and Image Recognition Unlike document image management, image processing involves image recognition, image enhancement, image synthesis, image reconstruction and image understanding. The original is not altered in document image workflow management system rather, annotations are recorded and stored separately an image processing system, on the other hand, may actually alter the contents of the image itself. Examples of image processing systems applications include recognition of images, as in factory floor quality assurance systems; image enhancement, as in 16 satellite reconnaissance systems; image synthesis, as in law enforcement suspect identification systems; and image reconstruction, as in plastic surgery design systems. Let us briefly review the various aspects of image processing and image recognition. Image enhancement: Most image display systems provide some level of image enhancement. This may be a simple scanner sensitivity adjustment very much akin to the light-dark adjustment in a copier. Increasing the sensitivity and contrast makes the picture darker by making borderline pixels black or increasing the gray-level of pixels. Or it may be more complex, with capabilities built in the compression boards. These capabilities might include the following: (i) Image calibration- the overall image density is calibrated, and the image pixels are adjusted to a predefined level. (ii) Real-time alignment- the image is aligned in real-time for skewing caused by improper feeding of paper. (iii) Gray-scale normalization- the overall level of an image is evaluated to determine if it is skewed in one direction and if it needs correction. (iv) RGB hue intensity adjustment- too much color makes picture garish and fuzzy. Automatic hue intensity adjustment brings the hue intensity within predefined ranges. (v) Color separation-A picture with very little color contrast can be dull and may not bring out the details. The hardware used can detect and adjust the range of color separation. Image Animation: Computer-created or scanned images can be displayed sequentially at controlled display speeds provide image animation that simulates real processes. Image animation is a technology that was developed by Walt Disney and brought into every home in the form of cartoons. The basic concept of displaying the successive images at short intervals to give the perception of motion is being used successfully in designing moving parts such as automobile engines. Image Annotation: Image Annotation can be performed in one of two ways: as a text file stored along with the image or as a small image stored with the original image. 17 Optical Character Recognition: Data entry has traditionally been more expensive component of data processing. OCR technology, used for data entry by scanning typed or printed words in a form, has been in use for quite some time. 1.6.3 Full motion Digital video Applications: Full motion video has applications in the games industry and training, as well as the business world. For all business applications, some core requirements are as follows:  Full-motion video clips should be sharable but should have only one sharable copy-user may have their own copies of design manual but storing duplicated video clips requires substantial storage.  It should possible to attach full-motion video clips to other documents such as memos, chapter text, presentations and so on.  Users should be able to take sections of a video clip and combine the sections with sections from other video clips to form their own video clips.  All the normal features of a VCR metaphor, such as, rewind, forward, play, and search should be available.  Users should be able to search to the beginning of a specific scene. That is, the full- motion video should be indexed.  Users should be able to place their own indexing marks to locate segments in the video clip.  Users should be able to move and resize the window displaying the video clip.  Users should be able to adjust the contrast and brightness of the video clip and also adjust volume of the associated sound. 1.6.4 Electronic messaging The first-generation mail systems provided a basic text link between users and provided a valuable communications medium for users within an enterprise. These systems were the first alternative to paper-based inter office memos. The second generation of E-mail systems expanded this capability tremendously by providing cross-platform and cross-network E-mail with a capability to attach other files ranging from editable text files to bit-mapped graphics and 20  Benefits also exist regarding photographs. Digital imaging will reduce the need for physical contact with original images. Furthermore, digital imaging creates the possibility of reconstructing the visual contents of partially damaged photographs, thus eliminating the potential that the original would be modified or destroyed.  Another advantage to digital photography is that it has been expanded to camera phones. We are able to take cameras with us wherever as well as send photos instantly to others. It is easy for people to us as well as help in the process of self-identification for the younger generation. 1.8 Summary This chapter introduced the definition of multimedia systems- the essential components of multimedia systems, benefits of multimedia systems in different areas, and the types of applications that fall into the class of multimedia. It also includes the digital imaging process. We listed text, graphics, images, fractals, audio, and video as the components that can be found in multimedia systems. Any multimedia design address how each of components will be handled. These must be addressed by applications such as, document imaging, image processing, full motion digital video applications, electronic messaging. We also addressed about the multimedia in learning-using of multimedia systems in different areas such as, relative industries, commercial uses, entertainment and fine arts, journalism, engineering, industry, mathematical and scientific research, medicine, document imaging. Here, have also discussed on the methods for creating digital images and the benefits of digital imaging. 1.9 Keywords: Multimedia, Text, Images, Sound, video, Elements of multimedia, Design of multimedia, Digital Imaging. 1.10 Exercises 1. Define multimedia. 2. List the multimedia elements. 3. Explain any two elements of multimedia system. 21 4. Discuss the applications of multimedia system. 5. What are the advantages of multimedia system? 6. Discuss briefly about Digital Imaging. 1.11 References 1. Ralf Steinmentz , klara Naestedt: Multimedia Fundamentals: Vol 1- Media Coding and Content processing, 2 nd edition, PHI, Indian Reprint 2008. 2. Prabhat K. Andleigh, kiran Thakrar,Multimedia Systems Design, PHI,2003. 3. Digital Multimedia, Nigel Chapman 22 UNIT-2 Structure 2.0 Objectives 2.1 Introduction 2.2 Types of Multimedia 2.4 Hypermedia and Multimedia 2.5 Multimedia and WWW 2.6 Different types of Digital media technology 2.7 History of color theory 2.8 Different types of Web graphics 2.9 Picture Archiving and Communication Systems 2.10 Summary 2.11 Keywords 2.12 Questions 2.13 References 2.0 Learning Objectives After studying this unit you will be able to,  Describe types of multimedia  Explain multimedia in different forms such as hypermedia, World Wide Web.  Describe different kind of media technologies.  History of color theory,  Explain Different types of web graphics, and Picture archiving and communication. 2.1 Introduction Before we get into the components and types of multimedia system, let‘s take a look at where the term multimedia originates. Multimedia once meant slide projector and a tape recorder being played simultaneously. For instance, 50 years ago, photographic images in slide form were projected on a screen or wall while audio attempted to synchronize with the sequence or played as ―background‖ music. In 1967 pop artist Andy Warhol organized ‗multimedia‘ events called the exploding plastic inevitable, where he showed films combined with live performances that were illuminated with 25 • Hypermedia is an application of multimedia, hence a subset of multimedia. 2.5 Multimedia and World Wide Web The WWW is the largest and most commonly used hypermedia application. Its popularity is due to the amount of information available from web servers, the capacity to post such information, and ease of navigating such information with a web browser. WWW technology is maintained and developed by the World Wide Web Consortium (W3C), although the Internet Engineering Task Force (IETF) standardizes the technologies. The W3C has listed the following three goals of WWW; universal access of web resources, effectiveness of navigating available information, and responsible use of posted material. 2.6 The different types of Digital media technology (i) Audio technology (ii) Graphics and images (iii) Computer-based animation (iv) Video technology 2.4.1 Audio technology Audiology is the discipline interested in manipulating acoustic signals that can be perceived by humans. Important aspects are psychoacoustics, music, the MIDI standard, and speech synthesis and analysis. Most multimedia applications use audio in the form of music and/or speech, and voice communication is of particular significance in distributed multimedia applications. Sound Sound is a physical phenomenon caused by vibration of a material, such as violin string or wood log. This type of vibration triggers pressure wave fluctuations in the air around the material. The pressure wave‘s propagates in the air. The pattern of this oscillation is called wave form. When hear a sound when such a wave reaches our ears. The Analog wave patterns have two attributes,  Volume – the height of each peak in the sound wave  Frequency – (sometimes referred to as pitch) the distance between the peaks. The greater the distance, the lower the sound. 26 Frequency A sound‘s frequency is the reciprocal value of its period. Similarly, the frequency represents the number of periods per second and is measured in hertz (Hz) or cycles per second (cps). A common abbreviation is kilohertz (kHz), which describes 1,000 oscillations per second, corresponding to 1,000Hz Sound processes that occur in liquids, gases, and solids are classified by frequency range:  Infrasonic: 0 to 20Hz.  Audiosonic: 20Hz to 20kHz  Ultrasonic: 20kHz to 1GHz  Hypersonic: 1GHz to 10THz. Amplitude A sound has a property called amplitude, which humans perceive subjectively as loudness or volume. The amplitude of a sound is a measuring unit used to derive the pressure wave from its mean value. Sound perception and psychoacoustics: Psychoacoustics is a discipline that studies the relationship between acoustic waves at the auditory ossicle and spatial recognition of the auditor. Two main perspectives: (i) The physical acoustic perspective. Figure 2-1 pressure wave oscillation in the air. 27 (ii) The psychoacoustic perspective. First wave-front law: this law says that an auditor‘s judgment about the direction of the acoustic event is primarily influenced by the sound that takes the shortest and most direct way. Digital Audio All multimedia file formats are capable, by definition, of storing sound information. Sound data, like graphics and video data, has its own special requirements when it is being read, written, interpreted, and compressed. Before looking at how sound is stored in a multimedia format we must look at how sound itself is stored as digital data. All of the sounds that we hear occur in the form of analog signals. An analog audio recording system, such as a conventional tape recorder, captures the entire sound wave form and stores it in analog format on a medium such as magnetic tape. Because computers are now digital devices it is necessary to store sound information in a digitized format that computers can readily use. A digital audio recording system does not record the entire wave form as analog systems do (the exception being Digital Audio Tape [DAT] systems). Instead, a digital recorder captures a wave form at specific intervals, called the sampling rate. Each captured wave-form snapshot is converted to a binary integer value and is then stored on magnetic tape or disk. Storing audio as digital samples is known as Pulse Code Modulation (PCM). PCM is a simple quantizing or digitizing (audio to digital conversion) algorithm, which linearly converts all analog signals to digital samples. This process is commonly used on all audio CD-ROMs. Differential Pulse Code Modulation (DPCM) is an audio encoding scheme that quantizes the difference between samples rather than the samples themselves. Because the differences are easily represented by values smaller than those of the samples themselves, fewer bits may be used to encode the same sound (for example, the difference between two 16-bit samples may only be four bits in size). For this reason, DPCM is also considered an audio compression scheme. One other audio compression scheme, which uses difference quantization, is Adaptive Differential Pulse Code Modulation (ADPCM). DPCM is a non-adaptive algorithm. That is, it does not change the way it encodes data based on the content of the data. DPCM uses the sample 30 introduction will only touch upon some of the most common formats. While not all formats are cross-platform, there are conversion applications which will recognize and translate formats from other systems. For example, the table 2-1 shows a list of file formats used in the popular Macromedia Director. File export File Import Image Palette Image .BMP, .DIB .PAL .BMP .GIF, .JPEG .ACT .PNG, .PSD .TIFF, .WMF Table 2-1: Different Image/graphics file formats There are two methods for representing and storing graphic/image data in uncompressed form, Bit-Map or Raster Images A bit-map representation stores the image by storing data about every dot/point of an image. These image points are termed pixels (a contraction for picture element). Vector / Structured Images A vector graphic file format does NOT store information about every pixel of a graphic. Instead a vector graphic file format is composed of analytical geometry formula representations for basic geometric shapes, (e.g., line, rectangle, ellipse, etc.). 1-Bit Images: Images consist of pixels or picture elements in digital images. A 1-bit image consists of on and off only and thus is the simplest type of image. Each pixel is stored as a single bit. Hence, such an image is also referred to as a binary image. It is also called a 1-bit monochrome image, since it contains no color. The following figure shows a 1-bit monochrome image 31 8-bit Gray-level image (256 gray value image) Now consider an 8-bit image that is, one for which each pixel has a gray value between 0 and 255. Each pixel is represented by a single byte, for example, a dark pixel might have a value of 10, and a bright one might be 230. The entire image can be thought of as a 2-dimensional array of pixel values. We refer to such an array as a bitmap,- a representation of the graphics/image data that parallels the manner in which it is stored in video memory. Figure 2-2: Representation of 1-bit image Figure 2-3: shows an example for1-bit Image Figure 2-4: Representation of 8-bit image 32 Image resolution refers to the number of pixels in a digital image. Fairly high resolution for such an image might be 1,600 * 1,200, whereas the lower resolution might be 640*480. Notice that here we are using an aspect-ratio of 4:3. We don‘t have to adopt this ratio, but it has been found to look natural. Each bit-plane can have a value of 0 or 1 at each pixel, but, together, all the bit-planes make up a single byte that stores values between 0 and 255. Figure 2-5: Example of a 256 gray value image Figure 2-6: Representation of Bit-planes 35 Color Lookup tables (LUTs) The idea used in 8-bit color images is to store only the index for code value, for each pixel. Then, e.g., if a pixel stores the value 25, the meaning is to go to row 25 in a color look-up-table (LUT). A Color-picker consists of an array of fairly large blocks of color (or a semi-continuous range of colors) such that a mouse-click will select the color indicated.  In reality, a color-picker displays the palette colors associated with index values from 0 to 255.  Each block of the color-picker corresponds to one row of the color LUT.  If the user selects the color block with index value 2, then the colormeant is cyan, with RGB values (0; 255; 255). (a) 24-bit color image (b) 8-bit color image Figure 2-9: Shows samples of 24-bitand 8-bit color images Figure 2.10: Color Lookup Table for 8-bit image 36 2.4.3 Video technology In addition to audio technology, TV and video technology form the basis of the processing of continuous data in multimedia systems. Video data can be generated in two different ways:  By recording the real world.  Synthesis based on a description. Basics The human eye is the human receptor for taking in still pictures and motion pictures. Its inherent properties determine, in conjunction with neuronal processing, some of the basic requirements underlying video systems. Representation of Video signals In conventional black-and-white television sets, the video signal is usually generated by means of a CRT. The representation of a video signal comprises three aspects; Visual representation, transmission, and Digitization. (i) Visual representation A key goal is to present the observer with as realistic as possible a representation of a scene. In order to achieve this goal, the TV picture has to accurately convey the spatial and temporal content of the scene. Important measures for this are:  Vertical details and viewing distance Figure 2.11: Color picker for 8-bit color. Each block of the color picker corresponds to one row color of the color LUT 37 The geometry of a television image is based on the ratio of the picture width W to the picture height H (W/H), called the aspect ratio. The Conventional aspect ratio is 4/3=1.33.The angular field of view is determined by the viewing distance, D, and is calculated as D/H.  Horizontal Detail and Picture Width The picture width used for television is 4/3 times the picture height. The horizontal field of view can be determined using the aspect ratio.  Total detail content of a picture The vertical resolution is equal to the number of picture elements of the picture height, while the number of horizontal picture elements is equal to the product of the vertical resolution and the aspect ratio.  Depth perception Depth is a result of composing a picture by each eye (from different angles). In a flat TV picture, a considerable portion of depth perception is derived from the Perspective appearance of the subject matter. Further, the choice of focal length of the camera lens and changes in depth focus influence depth perception.  Luminance and Chrominance RGB can be converted to a luminance (brightness signal) and two color difference signals (chrominance) for TV signal transmission  Temporal Aspects of Illumination Another property of human visual perception is the limit of motion resolution. In contrast to the continuous pressure waves of an acoustic signal, a discrete sequence of still images can be perceived as a continuous sequence. The impression of motion is generated by a rapid succession of barely differing still pictures (frames). Between frames, the light is cut off briefly. Two conditions must visual reality met in order to represent a visual reality through motion picture. First, the rate of repetition of the images must be high enough to ensure continuity of movements from frame to frame. Second, rate must be high enough so that the continuity of perception is not disrupted by the dark intervals between pictures  Continuity of Motion It is known that Continuous motion is only perceived as such if the frame rate is higher than 15 frames per second. To make motion appear smooth in a recorded film (not synthetically 40 Traditional cartoon animation is little more than a series of artwork cells, each containing a slight positional variation of the animated subjects. When a large number of these cells are displayed in sequence and at a fast rate, the animated figures appear to the human eye to move. A computer-animated sequence works in exactly the same manner. A series of images is created of a subject; each image contains a slightly different perspective on the animated subject. When these images are displayed (played back) in the proper sequence and at the proper speed (frame rate), the subject appears to move. Computerized animation is actually a combination of both still and motion imaging. Each frame, or cell, of an animation is a still image that requires compression and storage. An animation file, however, must store the data for hundreds or thousands of animation frames and must also provide the information necessary to play back the frames using the proper display mode and frame rate. Animation file formats are only capable of storing still images and not actual video information. It is possible, however, for most multimedia formats to contain animation information, because animation is actually a much easier type of data than video to store. The image-compression schemes used in animation files are also usually much simpler than most of those used in video compression. Most animation files use a delta compression scheme, which is a form of Run-Length Encoding (RLE) that stores and compresses only the information that is different between two images (rather than compressing each image frame entirely). RLE is relatively easy to decompress on the fly Storing animations using a multimedia format also produces the benefit of adding sound to the animation. Most animation formats cannot store sound directly in their files and must rely on storing the sound in a separate disk file which is read by the application that is playing back the animation. Animations are not only for entertaining kids and adults. Animated sequences are used by CAD programmers to rotate 3D objects so they can be observed from different perspectives; mathematical data collected by an aircraft or satellite may be rendered into an animated fly-by sequence. Movie special effects benefit greatly by computer animation. 41 2.7 History of Color Theory Color is a subject that can make your head spin. It's such a complex entity that we take for granted everyday as people and designers. The truth is there is a lot of science and color theory history behind it. This article briefly details some of the rich and interesting history behind color. Color Theory A major portion of art and design either relies on or utilizes color in some way and, at a first glance, color seems really easy to wield. But if you've tried serious coloring you might have realized that it difficult to get the colors to mesh or print correctly. This is because the way the eye perceives light as color and the way that substances combine to make color are different. Color theory is incredibly involved and has a lot different factors in a lot of different factors that make up color. Color theory has developed over time as different mediums such as pigments, inks, and other forms of media became more complex and easier to produce. There are currently 3 sets of primary colors depending on what materials are being used. Color Understanding how colors are defined in graphics data is important to understanding graphics file formats. In this section, we touch on some of the many factors governing how colors are perceived. How We See Color? The eye has a finite number of color receptors that, taken together, respond to the full range of light frequencies (about 380 to 770 nanometers). As a result, the eye theoretically supports only the perception of about 10,000 different colors simultaneously (although, as we have mentioned, many more colors than this can be perceived, though not resolved simultaneously). The eye is also biased to the kind of light it detects. It's most sensitive to green light, followed by red, and then blue. It's also the case that the visual perception system can sense contrasts between adjacent colors more easily than it can sense absolute color differences, particularly if those colors are physically separated in the object being viewed. In addition, the ability to discern colors varies from person to person; it's been estimated that one out of every twelve people has some form of color blindness. 42 Furthermore, the eye is limited in its ability to resolve the color of tiny objects. The size of a pixel on a typical CRT display screen, for example, is less than a third of a millimeter in diameter. When a large number of pixels are packed together, each one a different color, the eye is unable to resolve where one pixel ends and the next one begins from a normal viewing distance. The brain, however, must do something to bridge the gap between two adjacent differently colored pixels and will integrate average, ignore the blur, or otherwise adapt to the situation. For these reasons and others, the eye typically perceives many fewer colors than are physically displayed on the output device. How Colors Are Represented? Several different mathematical systems exist which are used to describe colors. This section describes briefly the color systems most commonly used in the graphics file formats. For purposes of discussion here, colors are always represented by numerical values. The most appropriate color system to use depends upon the type of data contained in the file. For example, 1-bit, gray-scale, and color data might each best be stored using a different color model. Color systems used in graphics files are typically of the tri-chromatic colorimetric variety, otherwise known as primary 3-color systems. With such systems, a color is defined by specifying an ordered set of three values. Composite colors are created by mixing varying amounts of three, which results in the creation of a new color. Primary colors are those which cannot be created by mixing other colors. The totalities of colors that can be created by mixing primary colors make up the color space or color gamut. Additive and subtractive color systems Color systems can be separated into two categories: additive color systems and subtractive color systems. Colors in additive systems are created by adding colors to black to create new colors. The more color that is added, the more the resulting color tends towards white. The presence of all the primary colors in sufficient amounts creates pure white, while the absence of all the primary colors creates pure black. Additive color environments are self-luminous. Color on monitors, for instance, is additive. 45 degree of self-luminescence of a color--that is, how much light it emits. A hue with high intensity is very bright, while a hue with low intensity is dark. HSV (also called HSB for Hue, Saturation, and Brightness) most closely resembles the color system used by painters and other artists, who create colors by adding white, black, and gray to pure pigments to create tints, shades, and tones. A tint is a pure, fully saturated color combined with white, and a shade is a fully saturated color combined with black. A tone is a fully saturated color with both black and white (gray) added to it. If we relate HSV to this color mixing model, saturation is the amount of white, value is the amount of black, and hue is the color that the black and white are added to. The HLS (Hue, Lightness, and Saturation) color model is closely related to HSV and behaves in the same way. There are several other color systems that are similar to HSV in that they create color by altering hue with two other values. These include:  HSI (Hue, Saturation, and Intensity)  HSL (Hue, Saturation, and Luminosity)  HBL (Hue, Brightness, and Luminosity) None of these is widely used in graphics files. YUV (Y-signal, U-signal, and V-signal) The YUV model is a bit different from the other colorimetric models. It is basically a linear transformation of RGB image data and is most widely used to encode color for use in television transmission. (Note, however, that this transformation is almost always accompanied by a separate quantization operation, which introduces nonlinearities into the conversion.) Y specifies gray scale or luminance. The U and V components correspond to the chrominance (color information). Other color models based on YUV include YCbCr and YPbPr. 46 Black, White, and Gray Black, white, and gray are considered neutral (achromatic) colors that have no hue or saturation. Black and white establish the extremes of the range, with black having minimum intensity, gray having intermediate intensity, and white having maximum intensity. One can say that the gamut of gray is just a specific slice of a color space, each of whose points contains an equal amount of the three primary colors, has no saturation, and varies only in intensity. White, for convenience, is often treated in file format specifications as a primary color. Gray is usually treated the same as other composite colors. An 8-bit pixel value can represent 256 different composite colors or 256 different shades of gray. In 24-bit RGB color, (12,12,12), (128,128,128), and (199,199,199) are all shades of gray. Table 2-2: Equivalent RGB, CMY, and HSV values RGB CMY HSV Red 255,0,0 0,255,255 0,240,120 Yellow 255,255,0 0,0,255 40,240,120 Green 0,255,0 255,0,255 80,240,120 Cyan 0,255,255 255,0,0 120,240,120 Blue 0,0,255 255,255,0 160,240,120 Magenta 255,0,255 0,255,0 200,240,120 Black 0,0,0 255,255,255 160,0,0 White 255,255,255 0,0,0 160,0,240 47 2.8 Different types of Web Graphics (i) GIF (Graphic Interchange Format) Graphic Image File format uses a CLUT (color lookup table) to define the colors as though they were individual color chips, and only supports up to 256 colors per image. Although it can simulate continuous-tone colors by dithering, that‘s generally best left to the JPEG or PNG formats. GIF87a was the original Web graphic file format. The current version, GIF89a, supports 1-bit (jagged-edge) transparency, comments, and simple animation. GIF is rarely a good choice for non-Web use. Technically GIF and its LZW compression algorithm are ―lossless,‖ but since it supports indexed color only (8-bit or less). (ii) JPEG (Joint Photographic Experts Group) Since June 1982, Working Group 8 (WG8) of ISO has been working on standards for the compression and decompression of still images. In June 1987, ten different techniques for coding color and gray-scaled still images were presented. An adaptive transformation coding technique based on the Discrete Cosine Transform (DCT) achieved the best subjective results. JPEG applies to color and gray-scaled still images. Video sequences can also be handled through a fast coding and decoding of still images, a technique is called Motion JPEG. (iii) PNG (Portable Network Graphics) PNG, relatively recent substitute for GIFs (and some JPEGs) online. Many technical advantages, such as….  Lossless compression (which means you could use it as an editable format, although you probably shouldn‘t in most cases).  Multi-bit transparency map (alpha channel), even for photo-type images.  Metadata for color management (gamma and ICC color profile), although this is something of a tease since most browsers don‘t support those things.  Can hold either RGB data (like a JPEG) or indexed-color data (like a GIF) — but not CMYK, since that‘s designed for the Web, not for print. 50 provide a growing cost and space advantage over film archives in addition to the instant access to prior images at the same institution. Digital copies are referred to as Soft-copy.  Remote access: It expands on the possibilities of conventional systems by providing capabilities of off-site viewing and reporting (distance education, telediagnosis). It enables practitioners in different physical locations to access the same information simultaneously for teleradiology.  Electronic image integration platform: PACS provides the electronic platform for radiology images interfacing with other medical automation systems such as Hospital Information System (HIS), Electronic Medical Record (EMR), Practice Management Software, and Radiology (RIS).  Radiology Workflow Management: PACS is used by radiology personnel to manage the workflow of patient exams. 2.10 Summary This chapter described about the different types of multimedia, such as, hypermedia and interactive media. Hypermedia is the use of text, data, graphics, audio and video as elements of an extended hypertext system in which all elements are linked, where the content is accessible via hyperlinks, where as the interactive multimedia is allows the user to control, combine, and manipulate different types of media, such as text, sound, video, computer graphics, and animation. We also discussed in brief about different kind of media technology, such as Audio technology, Images and graphics, video technology and computer based animation. In audio technology, we have discussed about the representation of sound in the computer, compression and decompression of analog signals to digital signal by using PCM, DPCM, and ADPCM. In graphics and images we described a few characteristics of graphics and images. The video technology, it includes all about the representation of video signals. In the color theory, we described the representation of colors by using RGB, CMY and HSV and so on. The different types of web graphics for using to store the images in different formats, such as GIF, JPEG, PS, PSD, TIFF and so on. 51 2.11 Keywords Hypermedia, Interactive media, Audio, sound, frequency, Amplitude, Digital audio, Sampling. Sampling rate, PCM, DPCM, ADPCM, MIDI, 1-bit image, Gray-scaled image, Color image, CLUT, Video technology, Aspect ratio, Animation, RGB, HSV, YUV, GIF, JPEG, PNG, PS, PSD, EPS, Picture Archiving. 2.12 Exercises 1. Explain the different types of multimedia. 2. Differentiate between multimedia and hypermedia? 3. Discuss briefly the different types of media technologies. 4. Explain the different types of color models. 5. Explain different types of web graphics. 6. Discuss briefly about picture archiving and communication system. 2.13 References 1. Ralf Steinmentz , klara Naestedt: Multimedia Fundamentals: Vol 1- Media Coding and Content processing, 2 nd edition, PHI, Indian Reprint 2008. 2. Prabhat K. Andleigh, kiran Thakrar,Multimedia Systems Design, PHI,2003. 3. Ze-Nian Li-Mark S Drew, Fundamentals of Multimedia, PHI, New Delhi .2011. 4. Donald Hearn and M. Pauline Baker, computer graphics, 3rd edition, Pearson. 52 UNIT-3 Introduction to Imaging Graphics, and photography Structure 3.0 Objectives 3.1 Airborne Imaging 3.2 Popular file formats 3.3 Pixel phone 3.4 Pixel Art 3.5 Graphics chipset 3.6 Multimedia and Graphics 3.7 Advantages and Disadvantages of Graphics 3.8 Summary 3.9 Keywords 3.10 Questions 3.11 References 3.0 Learning objectives  Explain Airborne Imaging methodology  Describe popular file formats like Graphics Interchange Format, Joint Photographic Experts Group.  Describe about Pixel and Pixel Art and graphics chipset.  Discuss different types of graphics and the advantages and disadvantages of graphics. 3.1 Airborne Imaging: Airborne imaging is one kind of digital imaging technique, which is used to digitize the images that are taken by a hyper-spectral camera. Hyper-spectral imaging, like other spectral imaging, collects and processes information from across the electromagnetic spectrum. This means that the camera is able to scan the biochemical composition of crops, and deliver an overview of every constituent present. For example, an airborne camera capable of photographing the condition of certain crops over many acres of land could provide agriculturalists with the information they need to improve 55 The more pixels used to represent an image, the closer the result can resemble the original. The number of pixels in an image is sometimes called the resolution, though resolution has a more specific definition. Pixel counts can be expressed as a single number, as in a "three-megapixel" digital camera, which has a nominal three million pixels, or as a pair of numbers, as in a "640 by 480 display", which has 640 pixels from side to side and 480 from top to bottom (as in a VGA display), and therefore has a total number of 640 × 480 = 307,200 pixels or 0.3 megapixels. 3.3.1 Bits per pixel The number of distinct colors that can be represented by a pixel depends on the number of bits per pixel (bpp). A 1 bpp image uses 1-bit for each pixel, so each pixel can be either on or off. Each additional bit doubles the number of colors available, so a 2 bpp image can have 4 colors, and a 3 bpp image can have 8 colors:  1 bpp, 2 1 = 2 color(monochrome)  2 bpp, 2 2 = 4 colors  3 bpp, 2 3 = 8 colors . . .  8 bpp, 2 8 = 256 colors  16 bpp, 2 16 = 65,536 colors (High-color)  24 bpp, 2 24 ≈ 16.8 million colors(True-color) 3.4 Pixel Art Pixel art is a form of digital art, created through the use of raster graphics software, where images are edited on the pixel level. Graphics in most old computer console, graphic calculator and mobile phone video games are mostly pixel art. Image filters (such as blurring or alpha-blending) or tools with automatic anti-aliasing are considered not valid tools for pixel art, as such tools calculate new pixel values automatically, contrasting with the precise manual arrangement of pixels associated with pixel art. 56 3.4.1 Techniques Drawings usually start with what is called the Line-art, which is the basic line that defines the character, building or anything else the artist is intending to draw. Line-arts are usually traced over scanned drawings and are often shared among other pixel artists. Other techniques, some resembling paintings, also exist. The limited palette often implemented in pixel art usually promotes dithering to achieve different shades and colors, but due to the nature of this form of art this is done completely by hand. Hand-made anti-aliasing is also used. 3.4.2 Saving and compression Pixel art is preferably stored in a file format utilizing lossless data compression, such as run- length encoding . GIF and PNG are two file formats commonly used for storing pixel art. The JPEG format is avoided because its lossy compression algorithm is designed for smooth continuous-tone images and introduces visible artifacts in the presence of dithering. 3.4.3 Categories Pixel art is commonly divided into two-categories: Isometric and Non-Isometric. The Isometric kind is commonly seen in games to provide a three-dimensional view without using any real three-dimensional processing. The Non-isometric pixel art is any pixel art that does not fall in the isometric category, such as views from the top, side, front, bottom views. These are also called Plano-metric views. 3.4.4 Scaling When pixel art is displayed at a higher resolution than the source image, it is often scaled using the nearest neighbor interpolation algorithm. This avoids blurring caused by other algorithms, such as bilinear and bi-cubic interpolation—which interpolate between adjacent pixels and work best on continuous tones, but not sharp edges or lines. Nearest-neighbor interpolation 57 preserves these sharp edges, but it makes diagonal lines and curves look blocky, an effect called pixilation. 3.3.5 Uses Pixel Art is widely used in different areas as follows:  Pixel art was very often used in older computer and console video games. With the increasing use of 3D graphics in games, pixel art lost some of its use.  Sometimes pixel art is used for advertising too. One such company that uses pixel art to advertise is Bell. The group eBay specializes in isometric pixel graphics for advertising.  Icons for operating systems with limited graphics abilities are also pixel art. The limited number of colors and resolution presents a challenge when attempting to convey complicated concepts and ideas in an efficient way. On the Microsoft Windows desktop icons are raster images of various sizes, the smaller of which are not necessarily scaled from the larger ones and could be considered pixel art.  Modern pixel art has been seen as a reaction to the 3D graphics industry by amateur game/graphic hobbyists. 3.5 Graphics Chipset In order to have images appear on your computer screen, you need something that can convert binary data (that's all of those 0's and 1's) into a picture. Computers either have graphics capabilities already built in to do that, or you have to install a graphics card. For computers that do not already have graphics capabilities, the graphics card is where that translation from binary code to image takes place. A graphics card receives information sent from the processor (CPU) using software applications. The processor is the "central processing unit" (CPU or microprocessor). A graphics card uses four main components to complete its tasks: MOTHERBOARD: A motherboard is what allows all of the parts of a computer to receive electric power and communicate with one another. On most computers, the motherboard has sockets and slots where processors and the system's main memory are stored. It has memory chips and chipsets (which are simply groups of chips) and a clock generator which is a circuit 60 Hue (color) to represent two-dimensional or three-dimensional objects. Line Art is usually monochromic, although lines may be of different colors. Illustration is a visual representation such as drawings,, painting, photograph or other work of art that stresses subject more than form. The aim of illustration is to decorate a story, poem or picture of textual information. Graph is a type of information graphic that represents tabular numeric data. Charts are often used to make it easier to understand large quantities of data and the relationship between different parts of the data. Diagram is a simplified and structured visual representation of concepts, ideas, constructions, relations, and statistical data etc, used to visualize and clarify the topic. 3.7 Advantages and disadvantages of graphics Advantages The computer graphics are being used in many areas like,  High quality graphics displays of personal computer provide one of the most natural means of communicating with a computer.  It has an ability to show moving pictures, and thus it is possible to produce animations with computer graphics.  With computer graphics use can also control the animations by adjusting the speed, the portion of the total scene in view, the geometric relationship of the objects in a scene to one another, the amount of detail shown and so on.  The computer graphics also provides facility called update dynamics. With update dynamics it is possible to change the shape, color or other properties of the objects being viewed.  With the recent development of digital signal processing (DSP) and audio synthesis chip the interactive graphics can now provide audio feedback along with the graphical feedbacks to make the simulated environment even more realistic. Disadvantages 1. It is time consuming to make decisions, must be made in advance for layout, color, materials, etc. 61 2. Technical in nature - audience knowledge to interpret, or understand. 3. Costly - depending on the medium used (poster board, transfer letters, etc.). 3.7.1 Computer graphics applications Graphics is widely used in many applications like,  User interfaces: It is now well established fact that graphical interfaces provide an attractive and easy interaction between users and computers.  Plotting graphs and charts: In industry, business, government, and educational organizations, computer graphics are commonly used to create 2D and 3D graphs of mathematical, physical, and economic functions in the form of histograms, bars, and pie- charts. These charts and graphs very useful in decision making.  Computer-aided drafting and design: The computer-aided drafting is used to design components and system electrical, mechanical, electro-mechanical and electronic devices such as automobile bodies, structures of building, ships very large scale integrated chips, optical systems and computer networks.  Simulation and Animation: Use of graphics in simulation makes mathematical models and mechanical systems more realistic and easy to study. The interactive graphics supported by an animation software proved their in use production of animated movies and cartoon films.  Art and commerce: there is a lot of development in the tools provided by computer graphics. This allows user to create artistic pictures which express message and attract attentions. Such pictures are very useful in advertisements.  Cartography: Computer graphics is also used to represent geographic maps, weather maps, oceanographic maps, population density maps and so on.  Education training: Computer graphics is also used to generate models of physical aids. Models of physical systems, physiological systems, population trends or equipment, such as color-coded diagram can help trainees to understand the operation of the system. 62 3.8 Summary This unit described about the Airborne imaging, in which the images that are taken by hyper- spectral camera are converted into digital images. This means that the camera is able to scan the biochemical composition of crops, and deliver an overview of every constituent present. In this unit we also discussed about the popular image format such as, GIF, JPEG. The GIF images are compressed to 20 to 25 percent of their original size with no loss in image quality using a compression algorithm called LZW. An important point about JPEG‘s is that they are generally a lossy format, unless you use another variation that is lossless. We also discussed about the Pixels, representation of pixels in digital images as well as the pixels on output devices. Pixel Art is a form of digital art, created through the use of raster graphics software, where images are edited on the pixel level. This unit is also described about working of Multimedia chipsets in computer systems. Graphics are visual representations on some surfaces, such as, a wall, canvas, screen, paper, inform and so on. 3.9 Keywords Airborne imaging, GIF, JPEG, Pixel phone, Pixel Art, Graphics chipset, Graphics, Raster images, vector images. 3.10 Exercises 1. What is Airborne imaging? Explain briefly. 2. Discuss briefly about GIF and JPEG image formats. 3. What is pixel phone? 4. Explain briefly about Pixel Art. 5. What is graphics? What are the advantages and disadvantages of graphics? 6. Discuss the applications of computer graphics. 3.11 References 1. Ralf Steinmentz ,klaraNaestedt: Multimedia Fundamentals: Vol 1- Media Coding and Content processing, 2 nd edition, PHI, Indian Reprint 2008. 2. Prabhat K. Andleigh, kiranThakrar,Multimedia Systems Design, PHI,2003. 3. Ze-Nian Li-Mark S Drew, Fundamentals of Multimedia, PHI, New Delhi .2011. 4. Donald Hearn and M. Pauline Baker, computer graphics, 3rd edition, Pearson. 65 with airbrush lines, for example), yet still remain vectors and so be editable. Some software can do a good job of transforming a given bitmap into a vector graphic, though there is always a loss of detail involved. 4.1.2 Vector graphics editors A vector graphics editor is a computer program that allows users to compose and edit vector images interactively on a computer and save them in one of many popular vector graphics formats, such as EPS, PDF, WMF, SVG, or VML. Features of Vector Graphics  Some vector editors support animation, while others (e.g. Adobe Flash) are specifically geared towards producing animated graphics. Generally, vector graphics are more suitable for animation, though there are raster-based animation tools as well.  Vector editors are closely related to desktop publishing software such as Adobe InDesign or Scribus, which also usually include some vector drawing tools. Modern vector editors are capable of, and often preferable for, designing unique documents of up to a few pages; it's only for longer or more standardized documents that the page layout programs are more suitable.  Special vector editors are used for computer-assisted drafting. They are not suitable for artistic or decorative graphics, but are rich in tools and object libraries used to ensure precision and standards compliance of drawings and blueprints.  Finally, 3D computer graphics software such as Maya, Blender or 3D Studio Max can also be thought of as an extension of the traditional 2D vector editors, as they share some common concepts and tools. 4.2 Bitmap Graphics In Computer graphics, a raster graphics image, or bitmap, is a dot matrix data structures representing a generally rectangular grid of pixels, or points of color, viewable via a monitor, paper, or other display medium. Raster images are stored in image files with varying formats. A bitmap corresponds bit-for-bit with an image displayed on a screen, generally in the same format used for storage in the display's video memory, or maybe as a device-independent bitmap. 66 A bitmap is technically characterized by the width and height of the image in pixels and by the number of bits per pixel. Raster graphics are resolution dependent. They cannot scale up to an arbitrary resolution without loss of apparent quality. This property contrasts with the capabilities of vector graphics, which easily scale up to the quality of the device rendering them. Raster graphics deal more practically than vector graphics with photographs and photo-realistic images, while vector graphics often serve better for typesetting or for graphic design. Modern computer-monitors typically display about 72 to 130 pixels per inch (PPI), and some modern consumer printers can resolve 2400 dots per inch (DPI) or more; determining the most appropriate image resolution for a given printer-resolution can pose difficulties, since printed output may have a greater level of detail than a viewer can discern on a monitor. 4.2.1 Advantages of bitmaps  In paint programs, you see what you are getting, usually in real time when wielding a ―paintbrush‖.  When you use a scanner, the output will normally be a bitmap.  Much easier to create the appearance of ―natural‖ media, such as areas of water colors bleeding into each other.  More universally available interchange file formats; most bitmaps can be read by most bitmap-based software and certain file formats such as jpeg and png can be read and written by every paint program. This is not, unfortunately, the case with vector file formats where many programs can only deal with their own file formats and a very limited choice of others such as eps may be available. 4.2.2 Bitmap Editors Raster-based image editors, such as painter, Photoshop, and MS Paint, , revolve around editing pixels , unlike vector-based image editors, such as Xfig ,CorelDraw , Adobe Illustrator, which revolve around editing lines and shapes (vectors). When an image is rendered in a raster- based image editor, the image is composed of millions of pixels. At its core, a raster image editor works by manipulating each individual pixel. Most pixel-based image editors work using 67 the RGB color model, but some also allow the use of other color models such as the CMYK color model. Features of Bitmap graphics  Advanced raster editors (like Photoshop) use vector methods (mathematics) for general layout soften have special capabilities in doing so, such as brightness/contrast, and even adding "lighting" to a raster image or photograph.  Raster editors are more suitable forretouching, photo processing, photo- realistic illustrations, collage, and hand drawn illustrations using a graphics tablet. Many contemporary illustrators use Corel Photo Paint, Photoshop,and other raster editors to make all kinds of illustrations. 4.3 Different types of Digital Media Technology Uncompressed graphics data require substantial storage capacity, which is not possible in the case of uncompressed image data. Most compression methods address the same problems, one at a time or in combination. Most are already available as product. Others are currently under development or are only partially completed. While fractal image compression may be important in the future, the most important compression techniques in use today are JPEG for single image pictures. 4.3.1 JPEG (Joint Photographic Experts Group) Since June 1982, Working Group 8(WG8) of ISO has been working on standards for the compression and decompression of still images. In June 1987, ten different techniques for coding color and gray-scaled still images were presented. An adaptive transformation coding technique based on the Discrete Cosine Transform (DCT) achieved the best subjective results. This technique was then further developed with consideration paid to the other two methods. The coding known as JPEG (Joint Photographic Experts Group) is a joint project of ISO/IECJTC/SC2/WG10 and comissionQ.16 of CCITT SGVIII. Hence, the ―J‖ (from ―Joint‖) in JPEG-ISOtogether with CCITT. In 1992,JPEG became an ISO International Standard (IS). JPEG applies to color and gray-scaled still images. Video sequences can also be handled through a fast coding and decoding of still images, a technique known as Motion JPEG. Today, implementations of parts of JPEG already available, either as software-only packages or using 70 An image consists of at least one and at most N=255 components or planes, as shown a left side of Figure 4-4. These planes can be assigned to individual RGB (red, green, blue) colors, or to the YIQ or YUV signals, for example Figure 4-4 Uncompressed digital image. Each component is a rectangular array Xi * Yi of pixels (the samples).Figure 4-5 shows an image with three planes, each with the same resolution. X X X Y YY Y Y Figure 4-5 Example of JPEG image preparation with three components having the same resolution. The resolution of the individual components may be different. Figure 4-6 shows an image with three planes where the second and third planes have half of the first plane. A gray-scale image will, in most cases, consists of a single component, while RGB color image will have three components with the same resolution (same number of lines Y1 = Y2 = Y3 and the same number of columns X1 = X2 = X3). In JPEG image preparation, YUV color images with subsampling of the chrominance components use three planes with Y1 = 4Y2 = 4Y3 and X1 = 4X2 =4X3. A1A2 C1C2 B1B2 71 Figure 4-6 Example of JPEG image preparation with three components having different resolutions. Each pixel is represented by P bits with the values in the range from 0 to 2 p – 1. All pixels of all components of an image must have the same number of bits. The lossy modes of JPEG use a precision of either 8 or 12 bits per pixel. The lossless modes can use between 2 and 12 bits per pixel. If a JPEG application uses any other number of bits, the application itself must suitably transform the image to conform to the number of bits defined by the JPEG standard. Instead of the values Xi and Yi, the compressed data includes the values X (maximum of all Xi), as well as factors Hi and Vi for each plane. Hi and Vi represent the relative horizontal and vertical resolutions with respect to the minimal horizontal and vertical resolutions. Let us consider the following example from. An image has a maximum resolution of 512 pixels in both the horizontal and vertical directions and consists of three planes. The following factors are given: Plane 0: H0 = 4, V0 = 1 Plane 1: H1 = 2, V1 = 2 Plane 2: H2 = 1, V2 = 1 This leads to: X = 512, Y=512,Hmax = 4 and Vmax= 2 Plane 0: X0 = 512, Y0 = 256 Plane 1: X1 = 256, Y1 = 512 Plane 2: X2 = 128, Y2 = 256 72 Hi and Vi must be integers between 1 and 4. This awkward-looking definition is needed for the interleaving components. In the image preparation stage of compression, the image is divided into data units. The lossless mode uses one pixel as one data unit. The lossy mode uses blocks of 8*8 pixels. This is a consequence of DCT, which always transforms connected blocks. Up to now, the data units are usually prepared component by component and passed on in order to the following image processing. Within each component, the data units are processed from left to right, as shown in Figure 4-7. This is known as a non-interleaved data ordering. Figure 4-7 Non-interleaved processing order of data units when processing a single component. Due to the finite processing speed of the decoder, processing of data units of different components may be interleaved. If the non-interleaved mode were used for a very high- resolution. RGB-encoded image, during rendering the display would first show only red, then green, and finally the correct colors. Cs1: H1 = 2, V1 = 2 Cs2: H2 = 2, V2 = 1 Cs3: H3 = 1, V3 = 2 Cs4: H4 = 1, V4 = 1 75 4.3.1.2.1 Image processing The first step of image processing in the baseline mode, as shown in Figure 4-9, is a transformation coding performed using the Discrete Cosine Transform (DCT).the pixel values are shifted into the zero-centered interval(-128, 127). Data units of 8×8 shifted pixel values are defined by Syx, where x and y are in the range of zero to seven. The following FDCT (Forward DCT) is then applied to each transformed pixel value: 𝑆𝑣𝑢 = 1 4 𝐶𝑢𝐶𝑣 𝑆𝑦𝑥 7 𝑦=0 7 𝑥=0 𝑐𝑜𝑠 2𝑥 + 1 𝑢𝜋 16 𝑐𝑜𝑠 2𝑦 + 1 𝑣𝜋 16 Where: Cu, Cv = 1/√2 for u,v = 0; otherwise Cu, Cv = 1 Altogether, this transformation must be carried out 64 times per data unit. The result is 64 coefficients Suv. Due to the dependence of DCT on the Discrete Fourier Transform (DFT), which maps values from the time domain to the frequency domain, each coefficient can be regarded as a two-dimensional frequency. The coefficient S00 corresponds to the portion where the frequency is zero in both dimension. It is also known an DC-coefficient and determines the fundamental color of all 64 pixels of the data unit. The other coefficients are called as AC-coefficients. For later reconstruction of the image, the decoder uses the Inverse DCT (IDCT). The coefficients Suvmust be used for the calculation: 𝑆𝑥𝑦 = 1 4 𝐶𝑢𝐶𝑣𝑆𝑢𝑣 7 𝑣=0 7 𝑢=0 𝑐𝑜𝑠 2𝑥 + 1 𝑢𝜋 16 𝑐𝑜𝑠 2𝑦 + 1 𝑣𝜋 16 Where: Cu, Cv = 1/√2 for u,v = 0; otherwise Cu, Cv = 1 If the FDCT, as well as the IDCT, could be calculated with full precision, it would be possible to reproduce the original 64 pixels exactly. From a theoretical point of view, DCT would be lossless in this case. In practice, precision is limited and DCT is thus lossy. The JPEG standard does not define any specific precision. It is thus possible that two different JPEG decoder 76 implementations could generate different images as output of the same compressed data. JPEG merely defines the maximum allowable deviation. Many images contain only a small portion of sharp edges; they consist mostly of areas of a single color. After applying DCT, such areas are represented by a small portion of high frequencies. Sharp edges, on the other hand, are represented as high frequencies. Images of average complexity thus consist of many AC-coefficients with a value of zero. This means that subsequent entropy encoding can be used to achieve considerable data reduction. 4.3.1.2.2 Quantization Image processing is followed by the quantization of all DCT coefficients; this is a lossy process. For this step, the JPEG application provides a table with 64 entries. One for each of the 64 DCT coefficients. This allows each of the 64coefficients to be adjusted separately. The application can thus relative significance of the different coefficients. Specific frequencies can be given more importance than others depending on the characteristics of the image material to be compressed. The possible compression is influenced at the expense of achievable image quality. The table entries Qvu are integer values coded with 8 bits. Quantization is performed according to the formula: squv = 𝑟𝑜𝑢𝑛𝑑 𝑆𝑣𝑢 𝑄𝑣𝑢 The greater the table entries, the coarser the quantization.Dequantization is performed prior to the IDCT according to the formula: Rvu = Squv × Quv Quantization and dequantization must use the same tables. Figure 4-10 shows a greatly enlarged detail. The blocking and the effects of quantization are clearly visible. In Figure 4-10(b) a coarser quantization was performed to highlight the edges of the 8×8 blocks. 77 (a) (b) Figure 4-10 Quantization effect 4.3.1.2.3 Entropy Encoding During the next step, either the initial step of entropy encoding or preparations for the coding process, the quantized DC-coefficients are treated differently than the quantized AC-coefficients. The processing order of all coefficients is specified by the zig-zag sequence.  The DC-coefficients determine the fundamental color of the data units. Since this changes little between neighboring data units, the differences between successive DC- coefficients are very small values. Thus each DC-coefficient of the previous data unit, in Figure 4-11, and subsequently using only the difference. DCi-1DCi DIFF = DCi - DCi-1 Figure 4-11 Preparation of DCT DC-coefficients for entropy encoding. Calculation of the difference between neighboring values.  The DCT processing order of the AC-coefficients using zig-zag sequence as shown in Figure 4-12 illustrates that coefficients with lower frequencies are encoded first, followed blocki-1blocki 80 Progressive image presentation is achieved by expanding quantization. This is equivalent to layered coding. For this expansion, a buffer is added at the output of the quantizer that temporarily stores all coefficients of the quantized DCT. Progressiveness is achieved in two different ways:  Using spectral selection, in the first run only the quantized DCT-coefficients of each data unit‘s low frequencies are passed on to the entropy encoding. Successive runs gradually process the coefficients of higher frequencies.  In successive approximation, all of the quantized coefficients are transferred in each run, but individual bits are differentiated to their significance. The most significant bits are encoded before the least significant bits. Besides Huffman coding, arithmetic entropy coding can be used in the expanded mode. Arithmetic coding automatically adapts itself to the statistical characteristics of an image and thus requires no tables from the application. According several publications, arithmetic encoding achieves around five to ten percent better compression rate. Arithmetic coding is slightly more complex and its protection by patents must be considered. 4.3.1.4 Lossless Mode The lossless mode shown in figure 4-15 uses single pixel as data units during image preparation. Between 2 and 16 bits can be used per pixel. Although all pixels of an image must use the same precision, one can also conceive of adaptive pixel precision. Uncompressed Digitized Image Data Compressed Image Data Figure 4-15 Lossless modes, based on prediction. Prediction Technique Entropy Encoder Tables 81 In this mode, image processing and quantization use a predictive technique instead of transformation coding. For each pixel X as shown in Figure 4-16, one of eight possible predictors is selected. The selection criterion is the best possible prediction of the value X from the already known adjacent samples. A,B, and C. Table 4-1 lists the specified predictors. C B A X Figure 4-16 Basis of prediction in lossless mode. The number of the chosen predictor, as well as the difference between the prediction and the actual value, are passed to the subsequent entropy encoding, which can use either Huffman or Arithmetic coding. In summary, this mode supports two types of processing, each with between 2 and 16 bits per pixel. Each variant can use either Huffman coding or Arithmetic coding. Selection Value Prediction 0 No Prediction 1 X = A 2 X =B 3 X = C 4 X = A + B + C 5 X = A + (B –C)/2 6 X = B + (A – C)/2 7 X = (A+B)/2 Table 4-1 Predictors in lossless mode. 82 4.3.2 Graphics Interchange Format (GIF) GIF (Graphics Interchange Format) was developed by CompuServe and uses the LZW (Lempel- Ziv-Welch) compression method, which is lossless. This method of compression builds a color table for the image where each color value is assigned to pixels. This compression method makes this image format ideal for line art, logos or other simple images without gradients or varying color. In fact GIF comes in two flavors. The original specification GIF87a. The later version, GIF89a, supports simple animation via a Graphics Control Extension block in the data. It is worthwhile examining the file format for GIF87 in more detail, since many such formats bear a resemblance to it but have grown a good deal more complex than this ―simple‖ standard. For the standard specification, the general file format is as in FIG 4-17. The signature is 6 bytes: GIF87a; the Screen Descriptor is a 7-byte set of flags. A GIF87 file contains more than one image definition, usually to fit on several different parts of the screen. Therefore each image can contain its own color lookup table, a Local Color Map, for mapping 8 bits into 24-bit RGB values. The GIF file format is as shown below: Figure 4-17 General format of GIF. 85 these features, some keyboards have an ergonomic design (figure 4-20) that provides adjustments for relieving operator fatigue. For specialized tasks, input to a graphics application may come from a set of buttons, dials, or switches that select data values or customized graphics operations. Figure 4-21 gives an example of a button box and a set of input dials. Buttons and switches are often used to input predefined functions, and dials are common devices for entering scalar values. Numerical values within some defined range are selected for input with dial rotations. A potentiometer is used to measure dial notation, which is then converted to the corresponding numerical value. Figure 4-20 Ergonomically designed keyboard with removable palm resets. (a) (b) Figure 4-21 A button box (a) and a set of input details (b). 86 Joysticks Another positioning device is Joystick, which consists of a small, vertical lever mounted on a base. We use the joystick to steer the screen cursor around. Most Joysticks, such as the unit figure 4-22, select screen positions with actual stick movement; others respond to pressure on the stick. Some joysticks are mounted on a keyboard, and some are designed as stand-alone units. The distance that the stick is moved in any direction from its center position corresponds to the relative screen-cursor movement in that direction. Potentiometers mounted at the base of the joystick measure the amount of movement, and springs return to the stick to the center position when it is released. One or more buttons can be executed once a screen position has been selected. In another type of movable joystick, the stick is used to activate switches that cause the screen cursor to move at a constant rate in the direction selected. Eight switches, arranged in a circle, are sometimes are provided so that the stick can select any one of eight directions for cursor movement. Pressure-sensitive joysticks, also called isometric joysticks, have a non-movable stick. A push or pull on the stick is measured with strain gauges and converted to movement of the screen cursor in the direction of the applied pressure. Figure 4-22 A movable Joystick. Data Gloves Figure 4-23 shows a Data Glove that can be used to grasp a ―virtual object‖. The glove is constructed with a series of sensors that detect hand and finger motions. Electromagnetic coupling between transmitting antennas and receiving antennas are used to provide information about the position and orientation of the hand. The transmitting and receiving antennas can each 87 be structured as a set of three mutually perpendicular coils, forming a three-dimensional Cartesian reference system. Input from the gloves is used to position or manipulate objects in a virtual-scene. A two-dimensional projection of the scene can be viewed on a video monitor, or a three-dimensional projection can be viewed with a headset. Figure 4-23 A virtual-reality scene, displayed on a two-dimensional video monitor, with input from a data glove and a spaceball. Digitizers A common device for drawing, painting, or interactively selecting position is a Digitizer. These devices can be designed to input coordinate values in either a two-dimensional or three- dimensional space. In engineering or architectural applications, a digitizer is often usedto scan a drawing or object and input a set of discrete coordinate positions. The input positions are then joined with straight-line segments to generate an approximation of a curve or surface shape. One type of digitizer is the Graphic Tablet (also referred as data tablet), which is used to input two-dimensional coordinates by activating a hand cursor or stylus at selected positions on a flat surface. A hand cursor contains cross hairs for sighting positions, while a stylus is a pencil- shaped device that is pointed at positions on the tablet. Figures 4-24 and 4-25 show example of desktop and floor model tablets, using hand cursors that are available with two, four, or sixteen buttons. Examples of stylus input with a tablet are shown in Figure 4-26 and 4-27 uses electromagnetic resonance to detect the three-dimensional position of the stylus. This allows an artist to produce different brush strokes by applying different pressures to the tablet surface. Tablet size varies from 12 by 12 inches for desktop models to 44 by 60 inches or larger for floor models. Graphics tablets provides a highly accurate method for selecting coordinate positions, with an accuracy that varies from about 0.2mm on desktop models to about 0.05mm or less on larger models. 90 Touch panels As the name implies, touch panels allow displayed objects or screen positions to be selected with the touch of a finger. A typical application of touch panels is for the selection of processing options that are represented as a menu of graphical icons. Some monitors can be adapted for touch input by fitting a transparent device (Fig 4-30) containing a touch-sensing mechanism over the video monitor screen. Touch input can be recorded using optical, electrical, or acoustic methods. (a) (b) 4-29 plasma panels with touch screens. Optical touch panels employ a line of infrared light-emitting diodes (LEDs) along one vertical edge and along one horizontal edge of the frame. Light detectors are placed along the opposite vertical and horizontal edges. These detectors are used to record which beams are interrupted when the panel is touched. The two crossing beams that are interrupted identify the horizontal and vertical coordinates of the screen position selected. Positions can be selected with an accuracy of about ¼ inch. With closely spaced LEDs, it is possible to break two horizontal or two vertical beams simultaneously. In this case, an average position between the two interrupted beams is recorded. The LEDs operate at infrared frequencies so that the light is not visible is not visible to a user. Light Pens Figure 4-30 shows the design of one type of light pens. Such pencil-shaped devices are used to select screen positions by detecting the light coming from points on the CRT screen. They are sensitive to the short burst of light emitted from the phosphor coating at the instant the electron beam strikes a particular point. Other light sources, such as the background light in the room, are 91 usually not detected by a light pen. An activated light pen, pointed at a spot on the screen as the electron beam lights up that spot, generates as electrical pulse that causes the coordinate position of the electron beam to be recorded. As with cursor-positioning devices, recorded light-pen coordinates can be used to position an object or to select a processing option. Although light pens are still with us, they are not as popular as they once were since they have several disadvantages compared to other input devices that have been developed. For example, when a light pen is pointed as the screen, part of the screen image is obscured by the hand and pen. And prolonged use of the light pen cause arm fatigue. Also, light pens require special implementations for some applications since they cannot detect positions within black areas. To be able to select positions in any screen area with a light pen, we must have some nonzero light intensity emitted from each pixel within that area. In addition, light pens sometimes give false readings due to background lightning in a room. Figure 4-30 A light pen with a button activation. Voice Systems Speech recognizers are used with some graphics workstations as input devices for voice commands. The voice system input can be used to initiate graphics operations or to enter data. These systems operate by matching an input against a predefined dictionary of words and phrases. A dictionary is set up by speaking the command words several times. The system then analyzes each word and establishes a dictionary of word frequency patterns, along with the corresponding functions that are to be performed. Later, when a voice command is given, the system searches the dictionary for a frequency-pattern match. A separate dictionary is needed for each operator using the system. Input for a voice system is typically spoken into a microphone mounted on a 92 headset, as in Figure 4-31, and the microphone is designed to minimize input of background sounds. Voice systems have some advantage over other input devices, since the attention of the operator need not switch from one device to another to enter a command. Figure 4-31 A speech recognition system. 4.5 Video display devices Typically, the primary output device in a graphics system is a video monitor. The operation of most video monitors is based on the standard cathode-ray tube (CRT) design, but several other technologies exist and solid state monitors may eventually predominate. Refresh Cathode-Ray Tubes Figure 4-32 illustrates the basic operation of a CRT. The cathode ray tube (CRT) is a vacuum tube containing one or more electron guns (a source of electrons or electron emitter) and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam(s) onto the screen to create the images. The images may represent electrical waveforms (oscilloscope), pictures (television, computer monitor), radar targets or others. CRTs have also been used as memory devices, in which case the visible light emitted from the fluorescent material is not intended to have significant meaning to a visual observer. The CRT uses an evacuated glass envelope which is large, deep (i.e. long from front screen face to rear end), fairly heavy, and relatively fragile. As a matter of safety, the face is typically made of thick lead glass so as to be highly shatter-resistant and to block most X-ray emissions, particularly if the CRT is used in a consumer product. 95 Random-Scan displays When operated as a Random-scan display unit, a CRT has the electron beam directed only to those parts of the screen where a picture is to be displayed. Pictures are generated as line drawings, with the electron beam tracing out the component lines one after the other. For this reason, random-scan monitors are also referred to as vector displays (or stroke-writing displays or calligraphic displays). The component lines of a picture can be drawn and refreshed by a random-scan system in any specified order (fig 4-34). A pen plotter operates in a similar way and is an example of a random-scan, hard-copy device. Refresh rate on a random-scan systems depends on the number of lines to be displayed on that system. Picture definition is now stored as a set of line-drawing commands in an area of memory referred to as the display list, refresh display file, vector file, or display program. To display a specific picture, the system cycles through the set of commands in the display file, drawing each component line in turn. After all line-drawing commands have been processed, the system cycles back to the first line command in the list. Random-scan displays are designed to draw all the component lines in a picture 30 to 60 times each second, with up to 100,000 ―short‖ lines in the display list. When a small set of lines is to be displayed, each refresh cycle is delayed to avoid very high refresh rates, which could burn out the phosphor. Random-scan systems were designed for line-drawing applications, such as architectural and engineering layouts, and they cannot display realistic shaded scenes. Since picture definition is stored as a set of line-drawing instructions rather than a set of intensity values for all screen points, vector displays generally have higher resolutions than raster system. Also, vector displays produce smooth line drawings because the CRT beam directly follows the line path. A raster system, by contrast produced jagged lines that are plotted as discrete point sets. However, the greater flexibility and improved line-drawing capabilities of raster systems have resultant in the abandonment of vector technology. 96 (a) (b) (c) (d) Figure 4-34 A random-scan system draws the component lines of an object in ant specified order. Color CRT monitors A CRT monitor displays color pictures by using a combination of phosphors that emit-colored light. The emitted light from the different phosphors merges to form a single perceived color, which depends on the particular set of phosphors that have been excited. One way to display color pictures is to coat the screen with layers of different colored phosphors. The emitted color depends on how far the electron beam penetrates into the phosphors layers. This approach, called the beam-penetration method, typically used only two phosphor layers: red and green. A beam of sloe electrons excite only the outer layer, but a beam of very fast electrons penetrates through the red layer and excites the inner green layer. At intermediate beam speeds, combination of red and green light emitted to show two additional colors, orange and yellow. The speed of electrons, and hence the screen color at any point, is controlled by the beam acceleration voltage. Beam penetration has been inexpensive way to produce color, but only a limited number of colors are possible, and picture quality is not good as with other methods. Shadow-mask methods are commonly used in raster-scan systems since they produce much wider range of colors than the beam-penetration method. This approach is based on the way that we seem to perceive colors as combinations of red, green, and blue components, called the RGB color model. Thus, a shadow-mask CRT uses three phosphor color dots at each pixel position. 97 One phosphor dot emits a red light, another emits a green light, and the third emits a blue light. This type of CRT has three electron guns, one for each color dot, and a shadow-mask grid just behind the phosphor-coated screen. The light emitted from the three phosphors results in a small spot of color at each pixel position, since our eyes tend to merge the light emitted from the three dots into one composite color. Figure 4-35 illustrates the delta-delta shadow-mask method, commonly used in color CRT systems. The three electron beams are deflected and focused as a group onto the shadow mask, which contains a series of holes aligned with the phosphor-dot patterns. When the three beams pass through a hole in the shadow mask, they activate a dot triangle, which appears as a small color spot on the screen. The phosphor dots in the triangles are arranged so that each electron beam can activate only its corresponding color dot when is passes through the shadow mask. Another configuration for the three electron guns is an in-line arrangement in which the three electron guns, and the corresponding red-green-blue color dots on the screen, are aligned along one scan line instead of in a triangular pattern. This in-line arrangement of electron guns is easier to keep in alignment and is commonly used in high resolution color CRTs. We obtain color variations in a shadow-mask CRT by varying the intensity levels of the three electron beams. By turning off two of the three guns, we get only the color coming from the single activated phosphor (red, green, or blue). When all three dots are activated with equal beam intensities, we see a white color. Yellow is produced with equal intensities from the green and red dots only, magenta is produced with equal blue and red intensities, and cyan shows up when blue and green are activated equally. In an inexpensive system, each of the three electron beams might be restricted to either on or off, limiting displays to eight colors. More sophisticated systems can allow intermediate intensity levels to be set for the electron beams, so that several million colors are possible.