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1 color rein van den boomgaard. 2 color images 3.

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Presentation on theme: "1 color rein van den boomgaard. 2 color images 3."— Presentation transcript:

1 1 color rein van den boomgaard

2 2 color images

3 3

4 4

5 5 the physics of color Light is electromagnetic energy

6 6 spectral color vs object color Lamp object color beam color

7 7 light source sensor object object color

8 8

9 9 photoreceptors in the retina

10 10 photoreceptors in the retina In the retina photoreceptors measure the light

11 11 photoreceptors in the retina Rods for low light levels (only B/W) Cones for normal light levels for color detection Three types of cones sensitive to different wavelenghts

12 12 sensitivity of the cones L M S

13 13 example

14 14 'calculate' SML

15 15 color blindness (see Wikipedia) Protanopia: Lacking the long-wavelength sensitive retinal cones, those with this condition are unable to distinguish between colors in the green-yellow-red section of the spectrum. They have a neutral point at a wavelength of 492 nmthat is, they cannot discriminate light of this wavelength from white. Deuteranopia: Lacking the medium-wavelength cones, those affected are again unable to distinguish between colors in the green-yellow-red section of the spectrum. Their neutral point is at a slightly longer wavelength, 498 nm.

16 16 color blindness about 10 percent of males is colorblind it is wise to check your colors in design to see whether colorblind people can distinguish the important colors

17 17 colorimetrie De SML gevoeligheidscurves zijn pas enige tientallen jaren met enige nauwkeurigheid bekend. Kleursystemen zijn veel ouder Colormatching: gebruik menselijk oog als meetinstrument om zoveel mogelijk de subjectiviteit van de menselijke beoordeling uit te sluiten 'vragen' we de mens alleen over gelijkheid van kleuren te oordelen

18 18 color matching experiment

19 19 rgb color matching functions

20 20 xyz color matching matrix

21 21 XYZ color system

22 22 chromaticity coordinates

23 23 xy – chromaticity diagram

24 24 color reproduction Faithfull color reproduction is possible using any three colorimetric independent light sources. a1a1 a2a2 a3a3

25 25 color reproduction

26 26 color reproduction a1a1 a2a2 a3a3

27 27 color gamut

28 28 color gamut

29 29 different color gamuts

30 30 RGB cube

31 31 RGB to XYZ

32 32 the RGB color cube

33 33 the RGB color cube

34 34 the RGB color cube

35 35 color camera’s a color CCD camera is either: 3 ‘parallel’ camera’s, one for Red, one for Green and one for Blue, or 3 ‘interwoven’ camera’s (Red, Green and Blue pixels mixed on the CCD: this is a lot like the human retina)

36 36 3 CCD color camera

37 37 Bayer color mosaic

38 38 finding Waldo

39 39 punctal COLOR observations

40 40 skin color

41 41 skin pixels, not-skin pixels RGB - space versus rgb - space skin color

42 42 skin color

43 43 hue – saturation – value hue: the dominant color (red/green/blue/...) saturation: pure color (saturation = 1) or almost colorless (mixed with grey: saturation = 0) value: the intensity (what you would see with a black and white camera)

44 44 hue – saturation – value

45 45 hue – saturation – valueB G R H S

46 46 hueB G R H S

47 47 color (hue) histogram


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