[Bug 1669734] Re: Quality decrease in libgd3 with upgrade to 2.1.1-4ubuntu0.16.04.5

[Ewald Stangl]

Since the last upgrade of the php7.0-gd package the workaround with the
old version doesn't work perfectly anymore.

Using the new php7.0-gd with the old libgd3 creates bad borders on some images.
With the current libgd3 this behavior doesn't appear, but the strange background isn't fixed yet.

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Title:
  Quality decrease in libgd3 with upgrade to 2.1.1-4ubuntu0.16.04.5

Status in libgd2 package in Ubuntu:
  Confirmed

Bug description:
  Hello,

  I use GD for resizing/branding images in PHP.
  Everything worked fine with libgd3 <= 2.1.1-4build2

  Since libgd3=2.1.1-4ubuntu0.16.04.5 there is a strange behavior when resizing transparent images with imagecopyresampled and putting them on a background.
  A simple code example:

  <?php
  $outImage = imagecreatetruecolor(200, 200);

  $color = imagecolorallocate($outImage, 233, 224, 218);
  imagefilledrectangle($outImage, 0, 0, imagesx($outImage), imagesy($outImage), $color);

  $im = imagecreatefrompng('https://www.expert24.com/200x.png');

  imagecopyresampled($outImage, $im, 50, 25, 0, 0, imagesx($outImage) -
  100, imagesy($outImage) - 50, imagesx($im), imagesy($im));

  imagepng($im);
  ?>

  
  With 2.1.1-4build2 everything looks fine but with newer versions there are stripes of a little darker color in the area of the transparent pixels of the overlayed image.

  The version of php-gd or the php version itself (5.6, 7.0 from main or
  ondrej-ppa) doesn't have any influence.

  The ubuntu changelog only says that there were some security fixes.

  Is there a workaround?

  
  regards
  Ewald Stangl

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