- No clues about the exact hardware procedure, though my emu runs 1 cycle of PPU, generates 1 background pixel (4 bits), it's ORed with color emphasis if required and transfered into a surface (bitmap). Once it's there, it can't be changed, since the palette is already loaded.
- My question is... Let's assume it's correct. If I change the palette, it's possible to plot another pixel using another color. In other words, it's possible to display all the possible NES colors in a single frame...?
Yes, it is possible for all colors to be drawn in a single frame with mid-frame palette updates. I believe there is a demo out there that demonstrates this.
Are you asking so you can find how deep your emulator's pixel buffer needs to be in order to emulate any possible NES program accurately? It is definitely possible to display all ~416 (52*8) colors on screen at once when PPU rendering is disabled (see
Full 410-Color NES Palette Demo). Once the pixel is output in the video signal, its color can't be changed, so you can think of your pixel map as the video signal.
Oh, I forgot that demo... thank you. ^_^;;
Anyway, the image on my emu looks ok. Is possible to count the number of colors using Photoshop as example?
If you don't plan on supporting NTSC artifacts (needed for correct background detail in Blaster Master), and you only support three different emphases in a single frame, then you can use a 256-color video output and still handle the vast majority of games correctly.
The image editor GIMP can tell you how many colors there are in an image, as long as there are 256 or fewer. Try converting the image to 256 color optimized palette, and then opening the "Colormap" window (called "Indexed Palette" in some versions).
Actually, if you go to Layers->Colors->Colorcube Analysis, you can see the number of different colors in any image, whether the image is 8-bit or not. I just tested it with a photo that has about 25000 different colors. This is in version 2.2.10, so it may have been moved to a different menu in newer versions.
Do any games actually use Color Emphasis bits, besides the "Dim the whole screen" mode used by Just Breed and others, and the Harry Potter pirate cartridge using Blue emphasis?
Final Fantasy cycles through color emphasis modes for the flashy effect in the battle transition.
I think I've read something about Noahs Ark that does some water effect with these bits(?)
Noah's ark appears to use the monochrome bit, possibly along with the color emphasis bits.
Dwedit wrote:
Noah's ark appears to use the monochrome bit, possibly along with the color emphasis bits.
Yes, it does. The water is monochrome with blue emphasis. Not the most realistic water effect in the world, but the best you can do on the NES without messing with the palette itself, something that would be way more complicated to do during rendering.