I've been beating my head against the problem of
getting transparent and non-transparent PNG thumbnails
to be the same color depth as the source image, to
resolve a couple issues:
* Thumbnails of palette (8-bit) PNG images are
currently truecolor, meaning the thumbnail is often
close to the same size (in bytes) as the full-size
image. The thumbnail should be the same color depth as
the source.
* PNGs with transparency, as a consequence, have
varying degrees of transparency (rather than simply
transparent/opaque), wreaking havoc with Internet
Explorer, which does not support them.
There is currently some discussion on the Village Pump
about my attempts at fixing these problems, by editing
includes/Image.php where the thumbnailing function
resides. I do not know for sure whether the GD
libraries or ImageMagick are currently in use in the
live version (ImageMagick was default on my
installation, and from what I can tell that's what's
used on the WP site). Because of the constraints of
both ImageMagick (can't create palette images from
truecolor) and the GD libs (a number of minor
annoyances that add up to major problems), I was
wondering whether it'd be okay to use a combination of
the two. My very first attempt at putting them both
together resulted in exactly what I was looking for.
ImageMagick resizes the image (preserving any
transparency), and the GD libs convert to palette.
Since I do not yet have CVS access, I am attaching a
diff against the 1.19 revision of includes/Image.php.
Again, I don't know if it's appropriate to use
ImageMagick and GD together, but it may solve a
problem that has been bothering quite a few people.
Eric
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