How to edit (existing) Game Boy Color palettes?

Discussion of development of software for any "obsolete" computer or video game system.
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marcosmoutta
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Joined: Mon Aug 17, 2020 1:41 pm

How to edit (existing) Game Boy Color palettes?

Post by marcosmoutta »

To keep it short - changing palettes in NES games is super easy, just open the PPU viewer in FCEUX, find the palette you want to change then write the new color over it in the hex editor.
I'd like to know how to do this for GBC. In particular, I'd like to change the colors of the Ghosts and Goblins port. It is very underrated, but the palettes look garish to compensate for the miserable screen found on real hardware.
Tried finding answers on google but could only find posts about colorizing DMG games. That's not what I care about.

Thanks
calima
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Re: How to edit (existing) Game Boy Color palettes?

Post by calima »

The principle is the same. The complications are also the same (if the game uses compression, etc etc, that simple approach won't work on either platform).
marcosmoutta
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Re: How to edit (existing) Game Boy Color palettes?

Post by marcosmoutta »

calima wrote: Wed Sep 21, 2022 12:41 am The principle is the same. The complications are also the same (if the game uses compression, etc etc, that simple approach won't work on either platform).
What I meant is, what emulator/software I use for this. Also I'm not sure how compression comes into play, I'm talking about changing palette values, not editing graphics.
The "simple approach" seems to work just fine on all NES games I tried, as long as I follow the instructions I reported

EDIT: BGB seems to do the trick. Just need to find a way to find the values for each color. This is easy on NES, there's like 50 total, but there's over 32 thousand on GBC

EDIT 2: http://www.budmelvin.com/dev/15bitconverter.html

EDIT 3: Hit another road block. Can't possibly figure out how the palettes are organized in ROM, or even where.
lidnariq
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Re: How to edit (existing) Game Boy Color palettes?

Post by lidnariq »

A better option is to use an emulator that accurately reproduces the actual colors of the screen, instead of the standard stupid emulator "what do you mean it's not sRGB?"
marcosmoutta
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Re: How to edit (existing) Game Boy Color palettes?

Post by marcosmoutta »

lidnariq wrote: Wed Sep 21, 2022 11:44 am A better option is to use an emulator that accurately reproduces the actual colors of the screen, instead of the standard stupid emulator "what do you mean it's not sRGB?"
I was doing this with the AGS101 in mind. Keyword: was. No idea how to proceed.
calima
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Re: How to edit (existing) Game Boy Color palettes?

Post by calima »

The dev-oriented emulators show you the palettes in hex, so you don't have to compare colors by eye. Just search for the hex numbers it gives. I can't tell you which GB emus do that unfortunately.
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tokumaru
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Re: How to edit (existing) Game Boy Color palettes?

Post by tokumaru »

marcosmoutta wrote: Wed Sep 21, 2022 8:24 amAlso I'm not sure how compression comes into play, I'm talking about changing palette values, not editing graphics.
Anything in a game may be compressed, not just graphics. I think that not many games used compressed palettes though, since they don't occupy that much space to begin with. But even if they're not compressed, that doesn't mean that you'll always find clean strings of color values stored one after the other in the ROM as they appear in video memory when the game is running. If a quick search for the values doesn't return anything, you'll probably have to debug the code that writes the values to video RAM, to try and locate where the values originally came from.
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