background colors for images

[Miles Bader]

Hi Gerd,

I don't know if you remember, but a long time ago, I suggested adding a
background-color field to `struct image', for those places in emacs that
want a single background color, such as when calculating the colors for
a 3d relief; if the image doesn't specify it directly, it should be
calculated heuristically using the `4 point' method.

You agreed that this was probably a reasonable idea.

So, attached, find my patch to implement this.  Could you tell me if it
looks reasonable?  It seems to work with all the tests I've done.

The most obvious problem this fixes is the little 3d checklist buttons
(made from a pixmap image) for the custom face-editor:  on a dark
background, these don't look 3d at all, but with my patch applied, they
do [actually the problem exists on a light background too, but it's much
more subtle -- if you look closely at the buttons, you'll the 3d relief
colors are appropriate for white buttons, not for grey75 buttons.]

Thanks,

-Miles

image-background.patch
Description: image-background.patch

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