Re: address@hidden: Re: problem with transparent PNG image display]

[Chong Yidong]

Richard Stallman <address@hidden> writes:

>     When no background color is saved in the image, we render using the
>     background color of the face the image is first drawn with, so the
>     problem is not immediately apparent with those images, but if you draw
>     the same image object onto a different colored background, you will see
>     the same problem occur.
>
> The cache could record what background color was used for rendering.
> Then, on displaying the image again, if the desired background is
> different, that could cause a cache-mismatch, which would cause
> re-rendering.

There is code to handle this in the trunk, but not in the branch.

I just changed the trunk code further to ignore the background color
specified by the png image (now that Emacs can properly handle
transparency, it is more correct to always use the frame background).

If you want this bug resolved for Emacs 22, it will be necessary to
port both changes from the trunk.  I think it should be moderately
safe.