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I'm having some trouble creating a clean looking image transcode from webp to jpeg using PHP's GD library. As a point of reference Here is a jpeg version of the original using Google's demo here: https://developers.google.com/speed/webp/gallery (I'm including this from the jpeg since I don't seem to be able to upload webp to stackoverflow)

enter image description here

First I tried this basic routine:

$image = imagecreatefromwebp('4.webp');
imagejpeg($image, 'converted.jpg', 100);

This kinda works but the result has a yellow background like this: enter image description here

I also tried using this bit of code for resizing images and drawing a white background first:

$image = imagecreatefromwebp('4.webp');
$width = imagesx($image);
$height = imagesy($image);
$new = imagecreatetruecolor($width, $height);
$background = imagecolorallocate($new, 255, 255, 255);
imagefilledrectangle($new, 0, 0, $width, $height, $background);
imagecopyresampled($new, $image, 0, 0, 0, 0, $width, $height, $width, $height);
imagejpeg($new, 'converted.jpg', 100);

This looks even worse and results in lots of strange artifacts:

enter image description here

Before I completely give up on GD can anyone make a suggestion to get this working properly? First and foremost, I'm looking for a solution using GD functions. If it's not possible I'm open to ImageMagick or another library - but I'd like a bit more insight into what's going wrong here and if it can be done correctly without changing tools.

But those new buttons though..
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  • Seems like something else is going on. When I run your basic routine it produced the expected image perfectly fine. No strange colors at all. – icecub Jan 07 '20 at 03:25

1 Answers1

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This may be caused by a well-known bug of an older implementation of LibGD in PHP: http://git.php.net/?p=php-src.git;a=commit;h=a31fe58d8005ff47f8f6ad095dcd4fb3a2f0aae9

https://bugs.php.net/bug.php?id=70102

From what I can see it was fixed in PHP 7.0.0: https://www.php.net/ChangeLog-7.php (bug 70102)

The second potential problem is libgd itselt. Before version 2.2.0 they have used libvpx, in 2.2.0 switched to libwebp.

I have reproduced the error with PHP 5.6.40 and LibGD 2.1.0. Then upgraded LibGD to 2.2.4 and all is working fine.

I suggest to upgrade to newer ubuntu, but you can also fetch all the required libraries manually from https://packages.ubuntu.com/search?keywords=libgd or by just increasing the version of the system in /etc/apt/sources.list, doing apt-get update and apt-get upgrade libgd-dev libgd (or libgd2 or libgd3 depending on the package name in your system - I am a Debian user, I do not actively follow Ubuntu packages). Most likely it will remove your php-gd lib so be sure to reinstall it too.

Bartosz Pachołek
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  • Ah that explains why it's working perfectly fine for me. I got my PHP version up to date. Nice find :) – icecub Jan 07 '20 at 03:26
  • Thank you - I'm using GD 2.1.1 and PHP 7.0.33-0ubuntu0.16.04.7. Your theory makes sense but I'm confused about why it would be affecting me with these versions. I can try upgrading PHP in the morning when I have time but it'd be nice to know for sure which version I should be targeting. – But those new buttons though.. Jan 07 '20 at 03:36
  • @billynoah Tested and working fine on PHP 7.2.24-0ubuntu0.18.04.1 You should probably upgrade your Ubuntu as well – icecub Jan 07 '20 at 03:51
  • @billynoah check my edit above: you are propably affected by the version of LibGD itself. I have replicated your exact error with 2.1.0 and got it solved with upgrade of just LibGD to 2.2.4. – Bartosz Pachołek Jan 07 '20 at 04:20