Stop GD insert filling watermark bbox with black (optimized)#1489
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insertTransparent() copied the base region into an opaque-black scratch canvas, layered the watermark on top, and merged it back with imagecopymerge(). Two problems: the black fill stuck wherever the base was transparent, so the watermark's bbox came out black on alpha PNGs; and imagecopymerge ignores source alpha, so partial watermark alpha was lost on the way back. Build a faded copy of the watermark by scaling each pixel's alpha by the transparency factor, then composite with imagecopy(). GD does the blending instead of imagecopymerge, so transparent base pixels stay put and partial watermark alpha survives. Regression test inserts circle.png on a 50x50 transparent canvas at transparency=0.5 and asserts the watermark's transparent corner is still transparent after insert. Also drop the unused CanConvertRange trait and the trailing imagedestroy() call (no-op since PHP 8.0).
olivervogel
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insertTransparent() copied the base region into an opaque-black scratch canvas, layered the watermark on top, and merged it back with imagecopymerge(). Two problems: the black fill stuck wherever the base was transparent, so the watermark's bbox came out black on alpha PNGs; and imagecopymerge ignores source alpha, so partial watermark alpha was lost on the way back.
Build a faded copy of the watermark by scaling each pixel's alpha by the transparency factor, then composite with imagecopy(). GD does the blending instead of imagecopymerge, so transparent base pixels stay put and partial watermark alpha survives.
Regression test inserts circle.png on a 50x50 transparent canvas at transparency=0.5 and asserts the watermark's transparent corner is still transparent after insert.
Also drop the unused CanConvertRange trait and the trailing imagedestroy() call (no-op since PHP 8.0).