人机接口与图形学(双语)06-Color.ppt

Hue色调 Saturation 饱和度 Lightness亮度 Pigments色素，颜料 tint色彩 tone色调 royal blue品蓝 Subjective主观的 Violet紫罗兰 Metamers条件等色 Flashback闪回，倒叙 Tristimulus三色刺激的 Cyan：青色 Cyan青色 magenta洋红 Precise Color Specifications Pigment-mixing is subjective depends on human observer, surrounding colors, lighting of the environment, etc We need an objective color specification Light is electromagnetic energy in the 400 to 700 nm wavelength range Dominant wavelength is the wavelength of the color we “see” Excitation purity is the proportion of pure colored light to white light Luminance is the amount (or intensity) of the light Electromagnetic Spectrum Visible light frequencies range between ... Red = 4.3 x 1014 hertz (700nm) Violet = 7.5 x 1014 hertz (400nm) Figures 15.1 from HB Visible Light Hue = dominant frequency (highest peak) Saturation = excitation purity (ratio of highest to rest) Lightness = luminance (area under curve) White Light Orange Light Figures 15.3-4 from HB How well do we see color? What color do we see the best? Yellow-green at 550 nm What color do we see the worst? Blue at 440 nm Flashback: Colortables (colormaps) for color storage Which RGB value gets the most bits? Can perceive color differences of 10 nm at extremes (violet and red) and 2 nm between blue and yellow Metamers – different energy radiations look like the same color Color perception also affected by surrounding light and adaptation Just noticeable difference (JND) 128 fully saturated hues can be distinguished Cannot perceive hue differences with less saturated light. Sensitivity to changes in saturation for a fixed hue and brightness ranges from 16 to 23 depending on hue. Talked about representing intensities last lecture Content Camera Models Color in Vision Color perception Color representations Human Color Vision Humans have 3 light sensitive pigments in their cones, called L, M, and S Each has a different spectral response curve: This leads to metamerism “Tristimulus” color theory Color Spaces Three ty