Скачать 640x400 Image Scrolling Example

15.03.1995
Скачать файл (282,47 Кб)

Some dood asked me a while ago 'bout some pascal examples
for scrolling huge image arrays in normal vga screen.
So, i make some.. for him and to test my friends 3d studio.
The biggest screen that you can scroll on normal vga card
(no svga) is 640x400. Why? cuz you have 64kb free memory
in 13h (320x200x256) mode. So, if u use chain-4 mode then
one byte plot 4 pixels, you can change what pixels must be
then plotted by setting planes.
So, if one byte sets 4 pixels then 64kb sets 320*200*4 pixels
and here you have 4 graphics pages!
But if you want to scroll 4 pages across then also you must
change screen width (notmal is 80 cuz 80*4=320) to 160
(160*4=640 - screen width). And then you can change position
in 640x400 screen by changing start screen offset.
So, that is all.. easy isn't it?
Sorry 4 that [english] language ;)