1. W2D1

2. HSV colour model Source: http://www.ncsu.edu/scivis/lessons/colormodels/color_models2.html Primary colours Red Green Blue Secondary Cyan Magenta Yellow Secondary=White-Primary (create colors for print)

3. W2D1 HSV colour model, tertiary colours Add the colours between primary and secondary

4. W2D1 HSV colour model Colour specified by 3 parameters: -hue (angle on disc) - saturation (how dominant is the hue relative to the other colours) -value (overall intensity of the light)

5. W2D1 HSV colour model

6. W2D1 Colour = sensation. It is determined by: -Light -Physiology -Psychology Experiment

7. W2D1 Read the colors of the words in col 1, then col 3, then col 2:

8. W2D1 http://www.michaelbach.de/ot/col_lilacChaser/index.html Experiments with optical illusions:

9. W2D1 9 Capturing images (with digital camera…) Charge motion Serial (horizontal) register Parallel (vertical) registers Pixel Image area (exposed to light) Output amplifier masked area (not exposed to light) (slides by Claudio Cumani, European Southern Observatory)

10. W2D1 Representing the intensity of a primary color (eg. Red) left: 3 bits per color (numbers 0 to 7) right: 8 bits per color (numbers 0 to 255)

11. W2D1 Lossless compression original x by y pixels stored: the color of every pixel, row by row

12. W2D1 Lossless compression original x by y pixels stored: the color of every pixel, row by row A lot of black pixels! (R,G,B=0,0,0) Replace sequence of black pixels by 2 numbers: “0, n” n - nr repetitions.

13. W2D1 Image from a digital camera (10MB) stored as 128kB

14. W2D1 8x8 blocks of pixelsJPEG compression

15. W2D1 <- 1 block.

16. W2D1 We can store the average value for every block

17. W2D1 What if we stored the average for 4x4 blocks?