phatch-dev team mailing list archive

[Nadia Alramli <nadiana@xxxxxxxxx>]

Hey Erich,

Sorry, It took me sometime to get back to you on this. I needed to play with
convert a bit to make sure I have the right answer.


> In PIL.Image.Image._new, which is what actually provides the new image when
> convert() is called, a type 'P' Image object will be assigned a new color
> palette.  This color palette has no relation to the color palette of the
> actual image. (I consider this to be a very serious bug in PIL).
>
I agree, those bugs are really annoying.


>   So what I do is get the palette from the converted image, and assign that
> to the Image.palette.palette.
>
>
>
> Secondly, since the color palette is most likely different after hte
> conversion, a simple index will not work. Instead save the transparent color
> value by looking up the index for it in the original palette. When the new
> palette is assigned, I then search for the transparent color value and save
> the appropriate index in the info['transparency'] attribute.
>
I can see a possible issue here. The colors in the palette are not
necessaryly unique. So it is possible to match the wrong index. In my
opinion a simpler solution is to create the new image in mode 'RGBA' instead
of 'RGB'. The GIF transparency will be kept this way. Then to convert from
RGBA to P you can use the updated solution here:
http://nadiana.com/pil-tips-converting-png-gif#Thesolution
I updated the article with a much better solution. I discovered it today
while playing with convert to find a solution for your issue.

I'm glad to have you in our team :)

Regards,
Nadia