Didn't suggest it until now as I didn't know of an algorithm that could do it, but now I do. This would make it easier to get images into a format usable by NM since you wouldn't need to manually change colors.
1. First split image imported into 8x8 segments. A single NES tile can be only 8x8 so it's good.
2. Now, for each segment get the 4 most used colors and turn the other into them by choosing the one closest to it. So if a block has 6 colors, like 32,45,255 22,34,125 0,20,0 23,44,0 23,136,234 and 32,45,33 with first 4 being the most common, all 23,136,234 pixels would become 22,34,125 and all 32,45,33 pixels would become 23,44,0
3. Next, replace most common colors with the back/rgb to conform with the internal format.
4. Combine the blocks together again in the same order they were originally in, possibly with black being the color used in the top-left pixel.
Still would require some fiddling to get right , but not nearly as much as it does now.
1. First split image imported into 8x8 segments. A single NES tile can be only 8x8 so it's good.
2. Now, for each segment get the 4 most used colors and turn the other into them by choosing the one closest to it. So if a block has 6 colors, like 32,45,255 22,34,125 0,20,0 23,44,0 23,136,234 and 32,45,33 with first 4 being the most common, all 23,136,234 pixels would become 22,34,125 and all 32,45,33 pixels would become 23,44,0
3. Next, replace most common colors with the back/rgb to conform with the internal format.
4. Combine the blocks together again in the same order they were originally in, possibly with black being the color used in the top-left pixel.
Still would require some fiddling to get right , but not nearly as much as it does now.