Page 39 - DCAP504_Computer Graphics

Computer Graphics

A 640-by-480 pixel screen displays 640 different dots on all 480 lines or about
307,200 pixels.

This translates into distinct dpi measurements depending on the size of the screen.

A 15-inch VGA monitor displays 50 dots per inch.

Did you know? Printers, monitors, scanners, and other input output devices are classified into high
resolution, medium resolution, and low resolution.
3.5.1 Underscan and Overscan

The underscan mode displays the full video frame, which discloses the content on the recorded edges,
but is not shown in the camera’s flip-out LCD. The overscan mode zooms on the field monitor into the
area that is visible on most of the televisions. The field monitor must be set to underscan mode if the
video is viewed on computer monitor or shown with a projector. The field monitor must be set to
overscan mode to check how the video is displayed on television.
The broadcast industry defined overscan as the central part of the image that can be viewed on a
standard television set. Underscan is the full frame, which is only seen on a production monitor. Hence,
the underscan shows the picture more clearly than the overscan.
3.5.2 Aspect Ratio

The aspect ratio of the image is the ratio of width of the image to the height of the image. Usually aspect
ratio is represented in two numbers separated by the colon.
If the aspect ratio of the image is X:Y, then 'X' is the width of the image and 'Y' is
the height of the image. Then, both the width and height are measured in the
same units.
If height is measured in inches then width is also measured in inches. Then, the
aspect ratio is mathematically expressed as X:Y or X x Y.

In televisions, DVDs and blue-ray convert the images of unequal sizes to the clear picture is done by
enlarging the image to fill the receiving format's area and deleting excess picture information. Different
factors of the image are changed and scaled through different factors to achieve the aspect ratio. Aspect
ratios are mathematically expressed as X:Y (pronounced "X-to-Y") and X x Y (pronounced "X-by-Y").
3.5.3 Measuring Color-depth and Computer Memory
Color-depth is the main factor on which resolution depends.

The three alternatives of color depth are:
1. 8-bit (256 colors)
2. 16-bit (65 thousand of colors)
3. 24/32-bit (16, 8 million colors)
Computer memory is measured in terms of bytes. Depending on the computer being used, screen
resolutions and color depth can be adjusted.
Graphics memory and resolution or color depth is interrelated. If the graphics memory of the computer
is known then the resolution or color-depths displayed by a computer can be calculated.

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