Bug #75124 [NEW]: gdImageGrayScale() may produce colors

From: cmb Operating system: * PHP version: 7.0.22 Package: GD related Bug Type: Bug Bug description:gdImageGrayScale() may produce colors Description: ------------ For ease of reference, I'm forwarding libgd bug #386[1]. TL;DR: gdImageGrayScale() misses to switch to gdEffectReplace alpha blending mode before calling gdImageSetPixel which may result in colored images. [1] <https://github.com/libgd/libgd/issues/386> Test script: --------------- <?php $im = imagecreatefrompng(__DIR__ . '/wings.png'); imagefilter($im, IMG_FILTER_GRAYSCALE); imagepng($im, __DIR__ . '/wings-out.png'); Expected result: ---------------- The generated wings-out.png should be a pure grayscale image. Actual result: -------------- The generated wings-out.png shows faintly purple colors. -- Edit bug report at https://bugs.php.net/bug.php?id=75124&edit=1 -- Try a snapshot (PHP 5.4): https://bugs.php.net/fix.php?id=75124&r=trysnapshot54 Try a snapshot (PHP 5.5): https://bugs.php.net/fix.php?id=75124&r=trysnapshot55 Try a snapshot (trunk): https://bugs.php.net/fix.php?id=75124&r=trysnapshottrunk Fixed in SVN: https://bugs.php.net/fix.php?id=75124&r=fixed Fixed in release: https://bugs.php.net/fix.php?id=75124&r=alreadyfixed Need backtrace: https://bugs.php.net/fix.php?id=75124&r=needtrace Need Reproduce Script: https://bugs.php.net/fix.php?id=75124&r=needscript Try newer version: https://bugs.php.net/fix.php?id=75124&r=oldversion Not developer issue: https://bugs.php.net/fix.php?id=75124&r=support Expected behavior: https://bugs.php.net/fix.php?id=75124&r=notwrong Not enough info: https://bugs.php.net/fix.php?id=75124&r=notenoughinfo Submitted twice: https://bugs.php.net/fix.php?id=75124&r=submittedtwice register_globals: https://bugs.php.net/fix.php?id=75124&r=globals PHP 4 support discontinued: https://bugs.php.net/fix.php?id=75124&r=php4 Daylight Savings: https://bugs.php.net/fix.php?id=75124&r=dst IIS Stability: https://bugs.php.net/fix.php?id=75124&r=isapi Install GNU Sed: https://bugs.php.net/fix.php?id=75124&r=gnused Floating point limitations: https://bugs.php.net/fix.php?id=75124&r=float No Zend Extensions: https://bugs.php.net/fix.php?id=75124&r=nozend MySQL Configuration Error: https://bugs.php.net/fix.php?id=75124&r=mysqlcfg