[Image-SIG] Applying a palette to an image

[Fredrik Johansson]

Hi,

Is there a way to apply a custom palette to an RGB-mode image using
PIL? I've looked at .putpalette and .convert and it seems there is
only support for either converting to the special web-safe palette or
generating a new palette based on the colors in the image.

I am writing a game editing application that is able to load images
from conventional files and convert them into a specialized format,
mapping colors to the game's pre-defined palette. Going from file to
raw bytes via PIL, and then through a routine that shuffles pixels
around to the specialized format, is fast enough even though the last
step is coded in Python. However, matching colors from a palette with
Python when starting from a 24-bit image is a serious bottleneck.

If there is any way this can be done with PIL that I've missed (I
wouldn't be surprised), information would be much appreciated. In case
there isn't, I might have to put the palette lookup code in a C
extension, which would be somewhat inconvenient. In that case, I'd
also take the opportunity to request humbly that this feature be
included in future versions of PIL.

Thanks,
Fredrik Johansson