1. Color Image Processing A spectrum of possibilities…

2. 9/17/2015Copyright GA Tagliarini, PhD 2 Spectral Model Of Light White light Infrared ultraviolet Sir Isaac Newton, 1666

3. 9/17/2015Copyright GA Tagliarini, PhD 3 Cone Cell Response Peak sensitivity cones – 65% red – 33% green – 2% blue Blue cones are most sensitive Observation is normally combination of colors Thomas Young, 1802

4. 9/17/2015Copyright GA Tagliarini, PhD 4 CIE Chromaticity Diagram Pure saturated colors lie along the edge and form a spectrum Colors on a line from the edge to equal energy change only saturation (l 1 ) Along a line between two internal points lie all colors that can be produced additively from the end-point colors (l 2 ) Within a triangle are all colors that can be produced additively from the three vertices Triangle shown is typical of the color characteristics, called the color gamut, of a video monitor l1l1 l2l2

5. 9/17/2015Copyright GA Tagliarini, PhD 5 RGB Color Cube Red Blue Green White Black Magenta Yellow Cyan Gray scale

6. 9/17/2015Copyright GA Tagliarini, PhD 6 Exercises Develop code to render an RGB color cube. Compare with G&W text Figure 6.8. How does the video rendering compare with a printed rendering? How many distinct colors can be represented if eight bits are used for each color dimension R, G, and B? Generate a “safe” color cube (recall that for safe colors the only allowable values for R, G, or B are 0x00, 0x33, 0x66, 0x99, 0xCC, and 0xFF) How many “safe” colors are there?

7. 9/17/2015Copyright GA Tagliarini, PhD 7 The HSI Color Model Hue—the color Saturation—the amount of white that is mixed with the hue Intensity—expresses the brightness or luminance of the chromaticity (=hue and saturation)

8. 9/17/2015Copyright GA Tagliarini, PhD 8 Converting from RGB to HSI

9. 9/17/2015Copyright GA Tagliarini, PhD 9 Converting from HSI to RGB Case R-G

10. 9/17/2015Copyright GA Tagliarini, PhD 10 Converting from HSI to RGB Case G-B

11. 9/17/2015Copyright GA Tagliarini, PhD 11 Converting from HSI to RGB Case B-R