Memory & Storage: Lesson 7 Storing Images, Slides of Computer science

Download Memory & Storage: Lesson 7 Storing Images and more Slides Computer science in PDF only on Docsity! Memory & Storage: Lesson 7 Storing Images Starter • Digital images can be stored on a computer in many different file formats • What are five different file formats that can be used? Memory & Storage: Lesson 7 Storing Images Image file types • BMP • JPG • GIF • PNG • TIF Memory & Storage: Lesson 7 Storing Images Types of Images Vector Image Bitmap Image • Made up of lines & shapes • Has properties such as line colour, fill colour etc… • These properties are stored in binary • Made up of pixels • Each pixel is a colour • Each colour is stored in binary https://www.youtube.com/watch?v=15aqFQQVBWU Memory & Storage: Lesson 7 Storing Images Bitmap (or Raster) images • Bitmap images are made up of PICture ELement or pixels • A pixel is the smallest identifiable area of an image • Each pixel is a single colour and is given a binary value which represents that colour e.g. 111100000000 might equal red • A pixel’s colour can be changed by changing this value Memory & Storage: Lesson 7 Storing Images Colour Depth How many bits are needed to store the different colours? To work out the minimum required colour depth, convert the number of colours to a power of 2. For up to: 2 colours- 1 bit required per pixel 4 colours: 2 Bits 8 colours: 3 Bits 16 Colours: 4 Bits 256 colours: 8 bits 65,536 colours: 16 bits Memory & Storage: Lesson 7 Storing Images Increasing the number of colours More bits per pixel = more colour combinations • 1 bit = 2 Colours • 2 bits = 4 Colours • 3 bits = 8 Colours • 4 bits = 16 Colours 00 = 11 = 01 = 10 = 10 10 10 10 10 10 11 01 11 11 01 11 01 01 01 01 01 11 01 01 01 01 01 11 01 00 00 01 11 11 11 11 01 00 00 01 11 11 11 11 01 00 00 01 01 01 01 01 Memory & Storage: Lesson 7 Storing Images Resolution • The quality of an image is dependent of its resolution. • Resolution is how many pixels can be displayed and how many bits are used to represent each pixel • Increasing colour-depth of an image and/or increasing resolution of an image increases the file size A picture which is 600 pixels wide and 400 pixels deep has a resolution of 600 x 400 Memory & Storage: Lesson 7 Storing Images Image resolution • Resolution is the concentration of pixels within a specific area • The area is defined by the image width and height in pixels e.g. 1920x1080 • 72 PPI (Pixels Per Inch) = typical screen resolution • 300 DPI (Dots Per Inch) = print quality resolution • Smartphones may have very high resolutions 300+ PPI 1x1 2x2 5x5 10x10 25x25 50x50 72x72 300x300 Memory & Storage: Lesson 7 Storing Images Calculating File Size To work out the file size of an image in bits, you need to: Resolution x colour Depth Example: An image with a resolution of 20 x 20 with a colour depth of 4 bits would be: 20 X 20 X 4 = 1600 bits or 200 bytes 20 pixels 2 0 p ix el s 8 colours Memory & Storage: Lesson 7 Storing Images Task 1: Storing Images Navigation: � Student G-Suite � Computer Studies � GCSE Computer Science � Unit 1: Computer Systems � 1.2: Memory & Storage � Lesson 7: Storing Images � Worksheet 1 Complete Task 1on the worksheet Memory & Storage: Lesson 7 Storing Images Storing Image Data • You can store image dimensions • You can change ‘colours’ by changing binary values Memory & Storage: Lesson 7 Storing Images Converting a bit pattern into a monochrome image Convert the following bit pattern into an 8x8 icon: 00000011 00000101 00001010 01010100 01101000 00110000 01011000 10000000 Memory & Storage: Lesson 7 Storing Images Colours • Each pixel has a proportion of red, green and blue • From a distance, it makes up one colour 181 Blue 126 Green 61 Red One pixel Memory & Storage: Lesson 7 Storing Images Colour Values 181m l Colour values of individual pixels are expressed as denary RGB values and in hexadecimal. Memory & Storage: Lesson 7 Storing Images Image metadata • Metadata is data about data • It is information other than image data that is stored with a file • This will include: • Colour depth in bits per pixel • Resolution (Height and width in pixels) • Date created • Author Memory & Storage: Lesson 7 Storing Images Task 2: Programming Images 1. Complete Task 2 on the worksheet 2. Complete page 82 in the CGP: Practice Exam Questions book • Use Page 73 in the CGP: Revision Guide book to help you Memory & Storage: Lesson 7 Storing Images Plenary • Fill in the gaps in each of the below sentences: • A bitmap graphic is made up of __________________ • Each _______ is represented in binary • The ________________________ determines the number of available colours for an image • Image _________ holds data about the image such as • ___________________________________________ • The greater the _________ of the image, the greater the file size