Grit - multi images, one palette?
Posted: Thu Nov 22, 2007 11:13 pm
I posted about this to the gbadev forums but it didn't get much of a response. I think it may be better off here anyway. I'm trying for no response on 2 forums, then I'll post it as a patch to the sf.net patch tracker 
I've been adding functionality to grit for converting several images but only generating a single (optimised) palette file. It is the one feature that I miss from gfx2gba. Grit's current behaviour is to create a 256-entry palette for each image. I realise that -pw or -pe can create smaller palettes, but that is no help in this case. The global palette option is if various images share some of their colours, not necessarily all, and there are up to 16 or 256 unique colours in total.
Here are the tech details.. The main design problem I've had has been that the current overall grit processing works something like this:
So the records don't know about their siblings and each one is destroyed after it generates its output. My change is to cache the records like this:
So I add a copy of all the GRIT_REC items to a vector, then use the _pal_rec from each of these to create an optimised global palette. Finally, I re-index the _img_rec.data using the optimised palette indices instead of each image's own palette. Obviously if there are more than 16/256 unique colours there isn't much it can do - it just prints an error and creates a palette with the extra colours missing. This was how gfx2gba worked and is the least hassle all round - let the user optimise colours using pixel editing programs, but let the tool generate useful palette information. Finally, it outputs the tile data, doesn't add palette info for the tiles, and outputs a global palette file.
I'm working on an NDS example or 2 as well, so I can test typical use cases.
Does that make sense to anyone? Is this something that would be of interest to people? I know I've used this a lot in the past. Oh, and is anyone working on adding this type of thing already? Wouldn't want to duplicate work, but I am *almost* done with it now.
I've been adding functionality to grit for converting several images but only generating a single (optimised) palette file. It is the one feature that I miss from gfx2gba. Grit's current behaviour is to create a 256-entry palette for each image. I realise that -pw or -pe can create smaller palettes, but that is no help in this case. The global palette option is if various images share some of their colours, not necessarily all, and there are up to 16 or 256 unique colours in total.
Here are the tech details.. The main design problem I've had has been that the current overall grit processing works something like this:
Code: Select all
for filename in filenames
{
GRIT_REC record = new GRIT_REC(filename)
process(record)
}
Code: Select all
vector<GRIT_REC> grv;
for filename in filenames
{
GRIT_REC record = new GRIT_REC(filename)
grv.push_back( record );
process(record)
}
COLOR global_palette[256];
for record in grv
{
for color in record.palette
{
if color not in global_palette
{
add_to_global_palette(color);
}
replace_index(old_palette_index, new_palette_index);
}
}
output(global_palette);
output(records in grv);
I'm working on an NDS example or 2 as well, so I can test typical use cases.
Does that make sense to anyone? Is this something that would be of interest to people? I know I've used this a lot in the past. Oh, and is anyone working on adding this type of thing already? Wouldn't want to duplicate work, but I am *almost* done with it now.