1. DATA REPRESENTATION IMAGES GCSE Computing

2. Learning Objective ■ To understand how an image is represented in Binary ■ To be able to convert a Binary code into an image. ■ Success Criteria ■ To be able to explain what a “pixel” is ■ To be able to explain what is meant by “colour depth” ■ To be able to view a simple Binary coded image

3. Pixels ■ When we take a photo with a digital camera, or download one from the Internet, it is saved in Binary code. ■ The image is made up with lots of tiny dots, which when viewed makes up the final image. ■ These are called Pixels:

4. Colour Depth ■ Each Pixel is coded in binary separately. ■ The code that we give it represents a colour. ■ For example, for a 2-bit coding we might have: ■ This system is said to have a colour depth of 2 bits/pixel. 00Pink 01Yellow 10White 11Green

5. Task: Decode the Image File ■ Use the colour map below to decode the image in question 4d) in your booklet: 00Pink 01Yellow 10White 11Green

6. Decoding the Image ■ The image in the previous example looks like this: ■ However in Binary form, it looks like this:

7. Quality? ■ You will notice this image is not very good. – It has not got many pixels – It has only got four colours. ■ It has got 11x8 (88) pixels, this is a very low- resolution. ■ The more pixels the image has, the higher the resolution is. ■ A normal digital camera might easily have 5 Mega (million) pixels and 24-bit colour depth! ■ This gives 125,829,120 binary bits for one photos!