Graphics Systems SUBJECT: COMPUTER GRAPHICS LECTURE NO: 02 BATCH: 16BS(INFORMATION TECHNOLOGY) 1/4/2019 1

Graphics Systems  Video display devices  Raster-scan systems  Random-scan systems  Graphics monitors and workstations  Input devices  Hard-copy devices  Graphics software 2 1/4/2019

Video Display Devices  Cathode-Ray Tube Monitor  Raster-Scan Displays  Random-Scan Displays  Color CRT Monitors  Direct-View Storage Tubes  Flat-Panel Displays  Three-Dimensional Viewing Devices 3 1/4/2019

Cathode-Ray Tube Monitor  The primary output device in a graphical system is the video monitor. The main element of a video monitor is the Cathode Ray Tube (CRT). 1/4/2019 4

Cathode Ray Tube  Heating Filament: Serves as heat source.  Cathode: Produces the electrons.  Control Grid: Controls the number of electrons that will be fired across "the gap”.  Focusing System: focusing the electrons into a beam.  Accelerating Anode: accelerate the electrons toward the front of the tube.  Horizontal Deflecting Plates: these plates move the electron beam, horizontally across the CRT screen.  Vertical Deflecting Plates: these plates move the electron beam up and down the screen. 5 1/4/2019

Raster Scan Displays  Devices that work on the algorithm of raster scan are called Raster Scan Displays.  In Raster Scan the process of displaying or capturing a video or image is done line by line.  Computer monitors and TVs use this method whereby electrons are beamed onto the phosphor creating on the screen a line at a time from left to right starting at the top-off corner. 1/4/2019 6

Raster Scan Displays 1/4/  Raster technique has some key terms:  Pixel  Frame Buffer  Pixmap  Bitmap  Horizontal and Vertical Retrace  Interlaced and Non-Interlaced

Key Terms Used in Raster Scans Pixel It is a minute area of illumination on a display screen, one of many from which an image is composed. Frame Buffer It is a portion of RAM containing a bitmap that is used to refresh a video display from a memory buffer containing a complete frame of data. Pixmap The term "pixmap" is short for "pixel map”. It stores and displays a graphical image as a rectangular array of pixel color values. 1/4/2019 8

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Key Terms Used in Raster Scans Horizontal Retrace At the end of the line, the beam is turned off and moved back to the left and down one line, which is known as Horizontal Retrace. Vertical Retrace When the bottom-right corner is reached, the gun is returned to the top-left corner, known as Vertical Retrace. Figure 1/4/

Key Terms Used in Raster Scans Non-Interlaced If you have a large image on your site and someone with a slower Internet connection comes to view that image, a non- interlaced image will simply be blank until the data transfers and then slowly it will appear from top to bottom. Interlaced An interlaced image will appear completely, but it will be highly pixelated. As the data transfers, the picture will begin to get clearer and clearer until the full resolution becomes apparent. Figure 1/4/

Raster Scan Displays  Conclusion:  Images Generated on Raster Scan Display Devices are Raster Images.  These Images are formed by illumination of spots called as PIXELS.  Each pixel contain information about each color, position and its brightness.  Thus, Raster Images are collection of a large number of pixels.  These Pixels are stored in BIT MAP of the image in the System Memory which is then viewed by the video controller. 1/4/

Cont..  Such Raster Images when Played in a Particular Sequence, it is called as Raster Animation Sequence.  Each Raster Image is called as Raster Frame.  Raster animation forms the more Realistic Real-time Images.  For sequence of such Raster Images, there is a Frame Buffer in System Memory that stores the Bit Map which is refreshed with a new bit map of new image that is to be displayed or sequenced:  The Figure Shows The scenario: 1/4/