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    <p>Here's some code that does work. Basically, it separates out the alpha channel, resizes the image using gamma correct, resizes the alpha channel <em>without</em> gamma correct, then copies over the alpha channel to the resized image that was done with gamma correct.</p> <p>My guess is that the imagegammacorrect() function has a bug. Perhaps gamma only applies to RGB and GD tries to do the same calculation to the alpha channel as well? Color theory is not my forte.</p> <p>Anyway, here's the code. Unfortunately I could not find a better way to separate out the channels than to loop over the pixels one-by-one. Oh well...</p> <pre><code>&lt;?php // Load image $image = imagecreatefrompng('test-image.png'); // Create destination $resized_image = imagecreatetruecolor(100, 100); imagealphablending($resized_image, false); // Overwrite alpha imagesavealpha($resized_image, true); // Create a separate alpha channel $alpha_image = imagecreatetruecolor(200, 200); imagealphablending($alpha_image, false); // Overwrite alpha imagesavealpha($alpha_image, true); for ($x = 0; $x &lt; 200; $x++) { for ($y = 0; $y &lt; 200; $y++) { $alpha = (imagecolorat($image, $x, $y) &gt;&gt; 24) &amp; 0xFF; $color = imagecolorallocatealpha($alpha_image, 0, 0, 0, $alpha); imagesetpixel($alpha_image, $x, $y, $color); } } // Resize image to destination, using gamma correction imagegammacorrect($image, 2.2, 1.0); imagecopyresampled($resized_image, $image, 0, 0, 0, 0, 100, 100, 200, 200); imagegammacorrect($resized_image, 1.0, 2.2); // Resize alpha channel $alpha_resized_image = imagecreatetruecolor(200, 200); imagealphablending($alpha_resized_image, false); imagesavealpha($alpha_resized_image, true); imagecopyresampled($alpha_resized_image, $alpha_image, 0, 0, 0, 0, 100, 100, 200, 200); // Copy alpha channel back to resized image for ($x = 0; $x &lt; 100; $x++) { for ($y = 0; $y &lt; 100; $y++) { $alpha = (imagecolorat($alpha_resized_image, $x, $y) &gt;&gt; 24) &amp; 0xFF; $rgb = imagecolorat($resized_image, $x, $y); $r = ($rgb &gt;&gt; 16 ) &amp; 0xFF; $g = ($rgb &gt;&gt; 8 ) &amp; 0xFF; $b = $rgb &amp; 0xFF; $color = imagecolorallocatealpha($resized_image, $r, $g, $b, $alpha); imagesetpixel($resized_image, $x, $y, $color); } } imagepng($resized_image, 'test-image-scaled.png'); ?&gt; </code></pre> <p>Replace hard-coded values with variables of course... And here's the result I get using your image and my code:</p> <p><a href="http://www.jejik.com/sander/test-image-scaled.png" rel="nofollow noreferrer">Resized image http://www.jejik.com/sander/test-image-scaled.png</a></p>
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    1. POPHP GD2: how to maintain alpha channel transparency and correct gamma
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    1. USSander Marechal
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    1. COinteresting, I'll have to spend some time with this tomorrow when I get back to the office :)
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    2. COhad a little refactoring to do in order to combine this with my existing code, but in the end it works great. Much appreciated!
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