Description:
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I wanted to create png image with imagepng(). It works fine but when I add third parameter (int $quality) it causes an zlib error.

Reproduce code:
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<?php

$image = imagecreatetruecolor(50, 50);
imagepng($image, null, 100);

Expected result:
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50x50px image with white background

Actual result:
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Warning: imagepng() [function.imagepng]: gd-png: fatal libpng error: zlib error in C:\var\www\laboratory\star\example.php on line 4

Warning: imagepng() [function.imagepng]: gd-png error: setjmp returns error condition in C:\var\www\laboratory\star\example.php on line 4