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Year 8 Unit 2 Bitmap Graphics

Learn about bitmap images, pixels, color depth, and resolution in digital graphics. Discover how binary numbers represent colors and set the color range in an image.

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Year 8 Unit 2 Bitmap Graphics

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  1. Year 8 Unit 2 Bitmap Graphics

  2. Today’s Aims 1 2 Start to grasp how colour depth sets the number of colours in an image 3 See links between how we use binary to handle numbers and colours Start to understand the terms bitmap, pixel and resolution

  3. Bitmaps Bitmap 3D Vector Shapes & fills Wireframes Pixels e.g. Clip art e.g. Movies e.g. Photos You know computers handle different kinds of images – but here’s what makes bitmaps special…

  4. Pixels Each pixel is a single colour So each colour needs its own binary code And there are a LOT of pixels in a photo… Are the tiny coloured squares that make-up bitmap images such as photos…

  5. Resolution So how many pixels in this tiny sample? 15 pixels 10 pixels 15 x 10 = ? pixels 150

  6. Resolution How many pixels in the whole photo? 2,345 pixels 2,345 x 3,519 = ? pixels 8,252,055 million 8 3,519 pixels megapixels 8

  7. 13 14 14 13

  8. We’ll make these notes Leave page blank Leave this page black 14 13

  9. 3. Bitmap Basics dd/mm/yy Images such as photos are called bitmaps. They are made from a grid of tiny squares called pixels. Each pixel’s colour is stored as a number in binary.

  10. Colour Depth How many colours could it use? White 0 Black 1 so can handle 2 colours 1 bit has 2 values Imagine a computer that works with just 1 bit

  11. Each pixel’s colour is stored as a number in binary. This example uses just one bit that’s either 0 or 1. So you can only have 2 colours e.g. black & white. To store more colours, you need more bits. This is called colour depth:

  12. Colour Depth How many colours could it now use? 0 0 0 1 1 0 1 1 White 0 0 Black 0 1 Blue 1 0 Red 1 1 so can handle 4 colours 2 bits have 4 values Now imagine the computer can use 2 bits

  13. Colour Depth How many colours could it now use? 0 0 0 0 0 1 0 1 1 0 1 0 1 1 1 1 White 0 0 Black 0 1 Spot anything familiar? Blue 1 0 Red 1 1 2 bits have 4 values Now imagine the computer can use 2 bits

  14. 0 0 0 1 1 0 1 1 Spot anything familiar? It’s that same binary number pattern!

  15. Colour Depth How many colours could it cope with now? 4s 2s 1s 0 0 0 =0 =1 0 0 1 0 1 0 =2 =3 0 1 1 1 0 0 =4 =5 1 0 1 1 1 =6 0 =7 1 1 1 so can handle 8 colours 3 bits have 8 values Next, what if the computer uses 3 bits

  16. Colour Depth How many colours could it cope with now? 0 0 0 White 0 0 0 0 0 1 Black 0 0 1 0 1 0 Blue 0 1 0 0 1 1 Red 0 1 1 1 0 0 Green 1 0 0 1 0 1 Orange 1 0 1 1 1 0 Yellow 1 1 0 1 1 1 Grey 1 1 1 so can handle 8 colours 3 bits have 8 values Next, what if the computer uses 3 bits

  17. Colour Depth bit colours 1 2 = x2 = colours bits 2 4 x2 = colours bits 3 8 x2 = colours bits 4 16 x2 = x2 colours bits 5 32 = x2 colours bits 6 64 = Spot anything else familiar? colours bits 7 128 x2 bits = colours 8 256 1 byte Do you recognise anumber pattern here?

  18. Colour Depth bit colours 1 2 = x2 = colours bits 2 4 x2 colours = bits 3 8 x2 colours = bits 4 16 x2 = colours x2 bits 5 32 = colours x2 bits 6 64 = colours Spot anything else familiar? bits 7 128 x2 bits = colours 8 256 1 byte Do you recognise a pattern here?

  19. x2 x2 x2 x2 x2 x2 128 64 32 16 8 4 2 1s 16s 4s 8s 2s 32s 128s 64s = ? 0 0 1 0 1 0 1 0 42 Spot anything else familiar? It’s that pattern of place values we used with binary!

  20. Colour Depth bit colours 1 2 = = colours bits 2 4 = colours bits 3 8 = colours bits 4 16 = colours bits 5 32 = colours bits 6 64 = colours bits 7 128 bits = colours 8 256 1 byte And here’s another way to show that same pattern… So this number pattern is all about doubling – again!

  21. 1 bit 2 bits 3 bits 4 bits 5 bits x2 x2 x2 x2 2 values 4 values 8 values 16 values 32 values Can you see the pattern here?

  22. 1 bit 2 bits 3 bits 4 bits 5 bits 6 bits 7bits 8 bits = 1 byte 8 bits x2 x2 x2 x2 x2 x2 x2 2 values 4 values 8 values 256 values 16 values 32 values ? values ? values ? values 64 values 128 values

  23. To store more colours, you need more bits. This is called colour depth: 1 bit = 2colours x2 2 bits = 4colours x2 3 bits = 8colours x2 4 bits = 16colours 5 bits = 32colours 6 bits = 64colours 7 bits = 128colours 8 bits = 256colours

  24. “Well done” Leave page blank This page is for the review 14 13

  25. Homework Review & learn 3. Bitmap Basics by creating a flipper Computing

  26. Review Leave page blank REVIEW ‘flipper’ 14 13

  27. Review Leave page blank REVIEW ‘flipper bitmap pixels colour depth binary 14 13

  28. bitmap pixels colour depth binary

  29. Define terms for homework pixels bitmap colour depth binary

  30. Homework Review & learn 3. Bitmap Basics by creating a flipper Computing Define & learn terms for homework

  31. Today’s Aims 1 2 Start to grasp how colour depth sets the number of colours in an image 3 See links between how we use binary to handle numbers and colours Start to understand the terms bitmap, pixel and resolution

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