31-Color Dual Plane Images
Posted: Sat Oct 12, 2019 8:16 am
Here's a demo of using two palettes on two planes, giving a maximum of 31 colors per tile.
We do this by optimizing an image down to 31 indexed colors. We then copy it into two files. On the first image, we convert the last 15 colors of the palette into black. On the second image, we convert the first 16 colors into black. We then reoptimize both down to have a unique 16 colors each, making sure that black is the first indexed color (and therefore the transparent color).
After that, it's just a matter of loading Image 1 into PLAN_A and Image 2 into PLAN_B.
A variant of this technique can use sprites as additional palette/layer, or adding shadow and highlights.
It's not as sophisticated as CRAM blast processing, but this is easy to set up. It lends well to certain types of images. I find the Orange+Blue+Dark Background images you see in posters work well with this.
PROS: Easy to set up; Minimized palette bleeding; Adds a bit more shading; Best for Title Screens, or cutscenes
CONS: Eats a lot of memory; 31 colors isn't that high of a color count; Might need lots of blank spaces in the image to save VRAM
We do this by optimizing an image down to 31 indexed colors. We then copy it into two files. On the first image, we convert the last 15 colors of the palette into black. On the second image, we convert the first 16 colors into black. We then reoptimize both down to have a unique 16 colors each, making sure that black is the first indexed color (and therefore the transparent color).
After that, it's just a matter of loading Image 1 into PLAN_A and Image 2 into PLAN_B.
A variant of this technique can use sprites as additional palette/layer, or adding shadow and highlights.
It's not as sophisticated as CRAM blast processing, but this is easy to set up. It lends well to certain types of images. I find the Orange+Blue+Dark Background images you see in posters work well with this.
PROS: Easy to set up; Minimized palette bleeding; Adds a bit more shading; Best for Title Screens, or cutscenes
CONS: Eats a lot of memory; 31 colors isn't that high of a color count; Might need lots of blank spaces in the image to save VRAM