1Raster GraphicsThomas FunkhouserPrinceton UniversityC0S 426, Fall 2000Overview• Display hardwareHow are images displayed?• Raster graphics systemsHow are imaging systems organized?• Color modelsHow can we describe and represent colors?2Overview• Display hardware How are images displayed?• Raster graphics systemsHow are imaging systems organized?• Color modelsHow can we describe and represent colors?Display Hardware• Video display devicesCathode Ray Tube (CRT)Liquid Crystal Display (LCD)Plasma panelsThin-film electroluminescent displaysLight-emitting diodes (LED)• Hard-copy devicesInk-jet printerLaser printerFilm recorderElectrostatic printerPen plotter3Cathode Ray Tube (CRT)Figure 2.4 from H&B Liquid Crystal Display (LCD)Figure 2.16 from H&B4Display Hardware• Video display devices» Cathode Ray Tube (CRT)» Liquid Crystal Display (LCD)Plasma panelsThin-film electroluminescent displaysLight-emitting diodes (LED)• Hard-copy devicesInk-jet printerLaser printerFilm recorderElectrostatic printerPen plotterOverview• Display hardwareHow are images displayed?• Raster graphics systemsHow are imaging systems organized?• Color modelsHow can we describe and represent colors?5Raster Graphics SystemsDisplayProcessorSystemMemoryCPUFrameBufferMonitorVideoControllerSystem BusI/O DevicesFigure 2.29 from H&B Frame BufferFrame BufferFigure 1.2 from FvDFH6Frame Buffer RefreshFigure 1.3 from FvDFH Refresh rate is usually 30-75HzColor Frame Buffer7Color CRTFigure 2.8 from H&B Overview• Display hardwareHow are images displayed?• Raster graphics systemsHow are imaging systems organized?» Color modelsHow can we describe and represent colors?8Electromagnetic Spectrum• Visible light frequencies range between ...Red = 4.3 x 1014 hertz (700nm)Violet = 7.5 x 1014 hertz (400nm)Figures 15.1 from H&BVisible Light• The color of light is characterized by … Hue = dominant frequency (highest peak)!Saturation = excitation purity (ratio of highest to rest)"Lightness = luminance (area under curve)White Light Orange LightFigures 15.3-4 from H&B9Color PerceptionFigure 13.18 from FvDFH Spectral-response functions of each of the three types of cones on the human retina.Tristimulus theory of colorColor Models• RGB• XYZ• CMY• HSV• Others10RGB Color ModelPlate II.3 from FvDFH R G B Color 0.0 0.0 0.0 Black1.0 0.0 0.0 Red0.0 1.0 0.0 Green0.0 0.0 1.0 Blue1.0 1.0 0.0 Yellow1.0 0.0 1.0 Magenta0.0 1.0 1.0 Cyan1.0 1.0 1.0 White0.5 0.0 0.0 ?1.0 0.5 0.5 ?1.0 0.5 0.0 ?0.5 0.3 0.1 ?Colors are additiveRGB Color CubeFigures 15.11&15.12 from H&B11RGB Spectral ColorsAmounts of RGB primaries needed to display spectral colors?Figure 15.5 from H&B XYZ Color Model (CIE)Amounts of CIE primaries needed to display spectral colorsFigure 15.6 from H&B CIE primariesare imaginary12CIE Chromaticity DiagramNormalized amounts of X and Y for colors in visible spectrumFigure 15.7 from H&B (White)CIE Chromaticity DiagramFigures 15.8-10 from H&BCompareColor GamutsIdentifyComplementaryColorsDetermineDominant Wavelengthand Purity13RGB Color GamutColor gamut for a typical RGB computer monitorFigure 15.13 from H&B CMY Color ModelPlate II.7 from FvDFH C M Y Color 0.0 0.0 0.0 White1.0 0.0 0.0 Cyan0.0 1.0 0.0 Magenta0.0 0.0 1.0 Yellow1.0 1.0 0.0 Blue1.0 0.0 1.0 Green0.0 1.0 1.0 Red1.0 1.0 1.0 Black0.5 0.0 0.0 ?1.0 0.5 0.5 ?1.0 0.5 0.0 ?Colors are subtractive14CMY Color CubeFigure 15.14 from H&B HSV Color ModelFigure 15.16&15.17 from H&B H S V Color 0 1.0 1.0 Red120 1.0 1.0 Green240 1.0 1.0 Blue * 0.0 1.0 White* 0.0 0.5 Gray * * 0.0 Black60 1.0 1.0 ?270 0.5 1.0 ?270 0.0 0.7 ?15Summary• Display hardware#Monitors: CRTs, LCDs, etc.$Hard-copy: printers, plotters, etc.• Raster graphics systems%Display processors&Frame buffers'Video controllers(Devices cannot display all visible colors• Color models)Tristimulus theory of color*Different color models for different devices, uses,
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