- Computer Graphics:- Computer Graphics is an technology that deals with the creation of pictures and images in computer. Generally, it refers to the computer generated images with the graphic software and hardware. Computer Graphics enables us to draw images for both 2-D as well as 3-D.
Some areas where Computer Graphics is used are Education and Training, Entertainment, Visualization, Image processing , Computer-Aided Design(CAD) etc.
- Refresh rate :- Refresh rate is the number of times a particular images is refreshed in computer system . The refresh rate is measured in hertz. For example , Refresh rate is 25 . It means that a image is refreshed 25 times in a second.
- Aspect Ratio :- It is a ratio of the vertical points to the horizontal points in order to produce a equal length line in both direction on screen. It is also defined as the ratio of width to height.
Aspect ratio = Width/Height
For example – An aspect ratio of 3/5 means that there are 3 vertical lines and 5 horizontal lines.
- Refresh buffer/ Frame Buffer :- Picture definition which is stored temporarily in a memory area of computer is called fame buffer. This area in computer stores the intensity values for a particular image.
- Retracing :- In Rastar and Random Scan Systems , the electron beam returns to the left of the frame at the end of each line to display the next line . This return to the left of the screen after refreshing each scan line is called horizontal retracing.
At the end of each frame , the electron beam returns to the start of the next frame i.e to the top left corner of the next frame . This retracing is called vertical retracing.
- Interlacing :- Interlacing is the technique of incrementally displaying a visual on a Cathode Ray Tube(CRT). In raster scan systems, each frame is displayed in two passes/intervals using an interlaced refresh procedure. The first pass seeps/completes the beam across every other scan line from top to bottom. Then after the vertical retrace, the beam sweep/completes out the remaining scan lines.
Question :-Consider 3 different raster systems with resolutions of 640 x 480, 1280 x 1024, and 2560 x 2048.
a) What size is frame buffer (in bytes) for each of these systems to store 10 bits per pixel?
Ans. Eight bits constitute a byte, frame-buffer sizes of the systems are as follows:
640 x 480 x 10 bits / 8 = 384KB;
1280 x 1024 x 10 bits / 8 = 1639KB;
2560 x 2048 x 10 bits / 8 = 6554KB;
Question :- Find out the aspect ratio of the raster system using 9 x 10 inches screen and 200 pixel/inch.
Ans. As we learnt above
Aspect ratio = Width/Height
= 9 x 200 /10 x 200 = 9/10
Aspect ratio = 9 : 10
Question :- Suppose the two raster systems having resolutions of 640 x 480 and 1280 x 1024.
a) How many pixels can be accessed per second in each of the systems that refreshes the screen at a rate of 60 frames per second?
Ans. Given, 60 frames are refreshed per second and each frame consists of 640 x 480 pixels, the access
rate of the first 640 x 480 is (640 x 480) * 60 = 1.8432 x 107 pixels/second.
Similarly, for the 1280 x 1024 system, the access rate will be (1280 x 1024) * 60 = 7.86432 x