Thanks VileRancour. I made another GWBASIC program that can display a .BMP file in color using the dithering technique. The .BMP files must have a 4bit palette (16 colors) and make use of the CGA composite colors. I converted some images to 160*200 .BMPs using Paint Shop Pro, so the actual image processing like scaling and anti-aliasing etc. is done in Paint Shop Pro; I'm not going to re-program all that (let alone in GW-BASIC). The image loading is pretty slow, oh well.. in dosbox you can speed it up by tapping CTRL-F12 a few times. See attachment for a zip with the BMPDITH.BAS and some .BMP example files.
I'm probably enjoying this CGA composite stuff a bit more than I should, but whatever (the GW-BASIC nostalgia is nice too btw
). It's just that I'm surprised that CGA was capable of more than the 4 colors with a horrible default color palette (magenta, cyan, white and black). Back in the mid-to-late 1980s, I used to play pc games on an EGA-adapter and CGA had always seemed pretty useless to me. And until now I never understood why some games supported a monochrome dithering mode, because that usually made the game look even worse on my EGA monitor. So this composite color-burst stuff is a bit of a "aha" moment for me.
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