For example VGA standard 35 Monitor The electrical signal triggers the pixel

For example vga standard 35 monitor the electrical

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For example, VGA standard 35
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Monitor The electrical signal triggers the pixel color. CRT and LCD technology has a limit on How small a pixel can be. How bright it can be How often it can be refreshed 60-90 Hertz is the typical range 36
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Data Color: Software The graphics card actually plugs into the mother board of the computer. The bit pattern travels across the motherboard . A device driver is used so that the operating system can communicate with the graphics card. A device driver is just small program…still written directly in assembly language. 37
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Graphics Cards Old graphics card were just signal converters New graphics cards have memory (RAM) and processors Takes the burden off of the computer’s processor. Enables 24-bit color at resolutions as high as 2560x1600. Plus graphics card can also do things like render vectors (geometry computations). 38
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RGB Color Depth Choose number of bits for each of R, G and B More bits per color means more total colors, but image files will be larger 8 bits per color is not the standard: 24-bit color, 16.7 million colors 0 255 218 39
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RGB Color Depth 8 bits (1 byte) per component means that you have 256 different “levels” If R = G = B, color is a shade of gray. Human eye can distinguish 256 shades of gray So, while 16.7 million colors is beyond what the human eye can distinguish. 24-bit RGB is under quantized for gray. But for Gray only. 40
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Practical Technique: Color Palettes Choose 256 most important colors in an image to store in its palette When 24-bit image is reduced to indexed color, some colors may be missing form the palette Replace missing color by nearest, may lead to posterization Dither – use pattern of dots and optical mixing Web-safe palette – 216 colors guaranteed to reproduce accurately on all platforms and browsers 41
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Alternative way of specifing colour Hue (roughly, dominant wavelength) Saturation (purity) Value (brightness) Model HSV as a cylinder: H angle, S distance from axis, V distance along axis Basis of popular style of colour picker HSV 173–176 42
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