The latest version of NES Screen Tool has improved BMP import features. I’m going to give them a try. The BMP must be a color indexed, 16 color, or 256 color. I think 16 color works better.
I found this image somewhere on the internet. I reduced the image to 256×240.
Using GIMP, first I adjusted the levels, especially the midtones, so they will not wash out.
My first attempt, I darkened the background and then converted to NES color (I previously made a custom palette using the NES palette). Then, Image/Mode/Indexed, and chose the NES palette. Then I Image/Mode/RBG. Then I Image/Mode/Indexed, Optimize to 16 color. Here’s what we have…
Then, I imported to NES Screen Tool, with only ‘lossy’ checked. This is what I got.
Ugh. Not great. Try again. Took the Original Image (256×240), leveled, with a darkened background…
Image/Mode/Grayscale, then Image/Mode/RGB. Then I selected the Pencil Tool (or brush), and changed it’s mode to ‘color’ and selected a Orange color, and recolored the gray image like a duotone. (I also adjusted the levels again).
Now…Image/Mode/Indexed, chose NES palette. Image/Mode/RGB. Image/Mode/Indexed, optimized for 4 color. Image/Mode/RGB. Image/Mode/Indexed, optimized for 16 color. (The NES Screen Tool seems to do better if you have the final in 16 colors).
This is what the final version looks like in GIMP. Let’s import BMP from NES Screen Tool again (only ‘lossy’ checked)… (and I touched up some tiles in NES Screen Tool).
Next time I’m going to import this as a background, compressed as an RLE file.