1. Skills: none Concepts: an image representation code, the number of bits in a code, the amount of information in an image This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License. Encoding images

2. Where does this topic fit? Internet concepts – Applications – Technology – Implications Internet skills – Application development – Content creation – User skills

3. Encoding image data Data typeDecade Numeric1950s Alphanumeric1960s Text1970s Image1990s Speech2000s Music2000s Video2000s HD video2010s

4. 010101011100101010101010101010111010 101010101010101010101010100101010101 000010110101010101010010101101101010 101010110010110010101010100101110101 001010010101010101010001001010101011 010011010010101010100101101001011100 101010101001010101000101010101010101 010010101001010101001001001001010101 001000101010101110100101001010101010 010101010101001010100100101010010101 001001010101001010100101010100101010 101001010101011110101011100001111011 All data is binary

5. Data + a code → information

6. Let’s encode this image

7. Each pixel has a color Each color has a code

8. 12 colors, 12 codes ColorCode Blue 0000 Light green 0001 Dark green 0010 Yellow 0011 Orange 0100 Red 0101 Purple 0110 Light grey 0111 Dark grey 1000 Brown 1001 Black 1010 White 1011

9. The image is 800 by 500 pixels

10. 0000 1011 0101 The codes for a few pixels

11. 800 pixels 500 pixels How much memory or storage?

12. 800 pixels 500 pixels 500 x 800 = 400,000 pixels 4x400,000 = 1,600,000 bits 1,600,000/8 = 200,000 bytes How much memory or storage?

13. Could we have had more than 12 colors? ColorCode Blue 0000 Light green 0001 Dark green 0010 Yellow 0011 Orange 0100 Red 0101 Purple 0110 Light grey 0111 Dark grey 1000 Brown 1001 Black 1010 White 1011

14. ColorCode Blue 0000 Light green 0001 Dark green 0010 Yellow 0011 Orange 0100 Red 0101 Purple 0110 Light grey 0111 Dark grey 1000 Brown 1001 Black 1010 White 1011 1100 1101 1110 1111 Four unused combinations

15. More bits means more unique codes A 00 B 01 C 10 D 11 A 0 B 1 A 000 B 001 C 010 D 011 E 100 F 101 G 110 H 111 A 0000 B 0001 C 0010 D 0011 E 0100 F 0101 G 0110 H 0111 I 1000 J 1001 K 1010 L 1011 M 1100 N 1101 O 1110 P 1111 1-bit code 2-bit code 3-bit code 4-bit code Do you see a pattern here?

16. A 000 B 001 C 010 D 011 E 100 F 101 G 110 H 111 Start with a three bit code What is the effect of adding a bit?

17. 000 001 010 011 100 101 110 111 Make two copies What is the effect of adding a bit? 000 001 010 011 100 101 110 111

18. 0000 0001 0010 0011 0100 0101 0110 0111 Add a zero to one copy and 1 to the other Doubling the number of possibilities What is the effect of adding a bit? 1000 1001 1010 1011 1100 1101 1110 1111

19. A 0000 B 0001 C 0010 D 0011 E 0100 F 0101 G 0110 H 0111 A 000 B 001 C 010 D 011 E 100 F 101 G 110 H 111 3-bit code 4-bit code I 1000 J 1001 K 1010 L 1011 M 1100 N 1101 O 1110 P 1111 Adding a bit doubles the number of codes

20. Color depth 8 bits per pixel → 256 colors 16 bits per pixel → 65.5 thousand colors 24 bits per pixel → 16.7 million colors 32 bits per pixel → 4.3 billion colors

21. 96% reduction – obvious information loss Both have the same number of pixels – explain the loss of information.

22. 1,080,000 pixels, no information

23. Pixels ↑ information ↑ Bits per pixel ↑ possible colors ↑ information ↑ The amount of information in an image

24. An image with a lot of information http://som.csudh.edu/fac/lpress/presentations/telegeography2010cablemap.jpg

25. Even more information http://www.dresden-26-gigapixels.com/dresden26GP

26. http://gigapan.org/ A library of information-rich images

28. Summary ColorCode Blue 0000 Light green 0001 Dark green 0010 Yellow 0011 Orange 0100 Red 0101 Purple 0110 Light grey 0111 Dark grey 1000 Brown 1001 Black 1010 White 1011

29. Self-study questions An image is 800 by 500 pixels, and each pixel can be one of 12 colors. How much memory would it require? An image is 800 by 500 pixels, and each pixel can be one of 256 colors. How much memory would it require? How many different colors could one represent using an 8 bit code? A nine bit code? Can you write a formula to compute the number of unique codes possible given the number of bits in a code?

30. Information rich images: http://www.dresden-26-gigapixels.com/dresden26GP http://som.csudh.edu/fac/lpress/presentations/telegeography2010cablemap.jpg http://gigapan.org/ http://gigapixel.com Resources