13. Architecture of simple Raster graphics system CPU System Memory System Bus I/O devices Video controller Monitor Frame buffer A fixed area of system memory reserved for frame buffer
14. Raster Scan Memory Requirements Interlacing * Even lines first * Odd lines next * 50 Hz to avoid flicker Memory Requirements depends on * resolution * colors, the system supports ex: For a resolution of 1024 * 768 Resolution with 8-bits per pixel( 256 colors ), it needs 768 Kb of memory.
15. Raster-Scan display processor CPU System Memory System Bus I/O devices Display processor memory Frame Buffer Video controller Display processor Monitor
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17. Raster Scan Generator X Register Y Register Memory Address Frame Buffer Pixel Register Horizontal and vertical deflection voltages Intensity Video controller addr (x,y) = base address + (x max – x min )(y – y min ) + ( x – x min )
18. Video controller Co- ordinate system Frame buffer locations are referenced in Cartesian co-ordinates. Co-ordinate origin * Lower left screen corner. * Upper left screen corner. Refresh operations of video controller Top-to-bottom , Left-to-Right X register(initial value = 0). Y register (initial value = y max )
21. 1 1-bit register black and white display 1 Digital-to-Analog converter Frame buffer screen
22. 2-bit register black , white - gray color display Digital-to-Analog converter Frame buffer screen 1 1 1 1
23. Frame buffer Digital to Analog converters 1-bit registers simple color graphics display COLOUR GUNS screen 1 0 1 1 1 0 RED GREEN BLUE
24. Frame buffer screen multi color grpahics display 3-bit registers COLOUR GUNS Digital to Analog converters RED GREEN BLUE 1 0 0 0 1 1 1 1 0
25. Frame buffer screen multi color grpahics display (Look-up tables) 3-bit registers COLOUR GUNS W-bit Digital to Analog converters W-bit Look-up table 2 n entries RED GREEN BLUE 1 0 1 0 1 1 0 1 0
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28. Random scan system CPU System Memory System Bus I/O devices Display processor Monitor Graphics commands are translated into a display file stored in the system memory.