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The Graphics Screen

by Mohsen Alshayef 24 Oct 2008

BBC BASIC for Windows provides keywords to perform graphics operations, such as plotting points, lines and circles, etc. These operations are performed using graphics coordinates into the graphics screen.

Irrespective of the graphics or display mode your programme is in, the reference graphics screen is made of a fixed coordinate system of -32768 to +32767 in the x- and y- directions.

The display mode selected then becomes a window into this large graphics screen. The example below illustrates mode 8 which has graphics units of 1280 x 1024.

In the example, a line is drawn between (-2500,-2000) and (2500,2500) using:

LINE -2500,-2000,2500,2500

and what would appear on the screen is only the portion of the line which crosses the window region.


Graphics Units should not be confused with Graphics Pixels (graphics resolution). The actual resolution (Graphics Pixels) of the screen modes is less than the corresponding Graphics Units. Typically, each graphics pixel translates into two (2) Graphics Units. An example of some screen modes are:

Mode
Graphaphics Units
Graphics Pixels
(Resolution)

8
1280 x 1024
640 x 512
14
2560 x 2048
1280 x 1024
20
1600 x 1200
800 x 600
22
2048 x 1536
1024 x 768
31
3200 x 2400
1600 x 1200


In the standard modes, each pixel translates into 2 Graphics Units wide and 2 Graphics Units High.

Details of screen modes may be found in the Manual at Graphics and Colours.

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the_20graphics_20screen.txt · Last modified: 2018/03/31 13:19 (external edit)