งานนำเสนอเรื่อง: "240-373 Image Processing1 Color Standards A pixel color is represented as a point in 3-D space. Axis may be labeled as independent colors such as R, G,"— ใบสำเนางานนำเสนอ:
Image Processing1 Color Standards A pixel color is represented as a point in 3-D space. Axis may be labeled as independent colors such as R, G, B or may use other independent indicators such as Hue, lightness, saturation. RBG, HSV, HSL are the most popular.
Image Processing2 RGB RGB (Red green blue) –For CRT display (TV, computer monitor) –Additive combination of r g and b
Image Processing3 HSV HSV (Hue Saturation Value) Hue is effectively a measure of the wavelength of the main color. It has a value between (0-360 o, Red = 0 o, Green=120 o and Blue=240 o.) Hue can be calculated from RGB values as follows: Rh = R - min (R, G, B) Gh = G - min (R, G, B) Bh = B - min (R, G, B) At least on of these values is 0. Hue value is in between.
Image Processing4 HSV For example if Rh = 0 Hue angle = (240xBh + 120xGh ) / (Bh + Gh) If two are zero, then hue is the angle corresponding to the third non-zero color. If three are zero, then there is no color hue. The monitor will display a gray level (between black and white).
Image Processing5 Saturation Saturation is the amount of pure hue in the final color If Saturation = 0, final color is without hue ( white light only) If Saturation = 255, no white light in final color Saturation = (max(R,G,B) - min (R,G,B)) / max(R,G,B)
Image Processing6 Value Value (brightness) is a measure of the intensity of the brightest component and given by Value = max(R,G,B)
Image Processing7 The HSV Model
Image Processing8 HSV Example Given R=100, G=200, B= 40, convert this RGB color model to HSV. Rh = min(100,200,40) = 60 G h = min (100,200,40) = 160 B h = 40 - min (100,200,40) = 0 H = (60* *(120*256/360))/(60+160)
Image Processing11 HLS HLS (Hue Lightness Saturation) Similar to HSV except that the hue angle start at Blue = 0 o, and the model is double cone with a lightness axis going from L=0 (black) to L=1 (white) For HLS, hue is calculated the same way as for HSV model except Blue = 0 and lightness and saturation are given by: Lightness = (max(R,G,B) - min(R,G,B))/2 (max+min)/(max-min) if L <= 0.5 Saturation = (max-min)/(2-max-min) otherwise
Image Processing15 The Human Vision Better than any camera yet developed Eye has 2 classes of discrete light receptors; Cones and rods 6-7 million cones, sensitive to bright light >= 75 Million rods, sensitive to light intensity but not color eye color perceptions
Image Processing16 Color Additive Problem with CRT