Posted By
MMS
on 2017-01-23
17:44:53
 |  Re: Colors area for Multicolor screen
Actually, I found a rather strange behaviour of the DRAW routine.
I loaded converted multi picture, and wanted to draw on it.
I tried to draw lines with Color 0, 1, 2, 3, and although color 0 and color 3 are global, the all the lines drawn messed up the attribute memory, instead of just setting the pixels to background0 or color3, as it should be (as they should not infuence the attribute clor/luminance map at all).
Even if the converted graphic has such a chaotic attribute settings, how the color3 line can influence it at ALL?
The DRAW routine should NOT write anything to the color / luminance memory, just to the bitmap when I draw with 0 or 3 color setting.
I tested YAPE and Plus4Emu, and they behave the same.
Please let me know if I missed a logical step or explanation there.
As you can see, it is a normal multiciolor bitmap, quickly converter to show the problem.
Trials and errors
I drew 4 lines, te first is with color 0 (background) is almost non visible, but messed up the attributes near to first wheen/tyre.
Then came the lines with Color1, then Color 2 and finally Color 3.
As you see, all had influence on the color attributes at some area, though color 0 and color 3 should not have any, just changing the bitmap's double pixel to the two color register's representative pixel pair value. Strange, yeah?
Maybe it could be a great improvement of the Plus4emu converter, if NO Color3 would be used AT ALL during conversion. sure, it would great ly reduce the color and fine details., but you could freely move a Color 3 object over the screen, like a soft-sprite.
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