Merge branch '2.1'

diff --cc wcfsetup/install/files/lib/system/image/adapter/GDImageAdapter.class.php
index 1cefdc211a5bc507a4a64f966612586ba7b38bab,0410dc387ed76f040a339b46fd3ef444968b9c2c..719cddcbdd2eb8ced20b4c68fe60d20112263315
--- 1/wcfsetup/install/files/lib/system/image/adapter/GDImageAdapter.class.php
--- 2/wcfsetup/install/files/lib/system/image/adapter/GDImageAdapter.class.php
+++ b/wcfsetup/install/files/lib/system/image/adapter/GDImageAdapter.class.php
@@@ -324,14 -326,16 +324,16 @@@ class GDImageAdapter implements IImageA
                
                ob_start();
                
+               imagealphablending($image, false);
+               imagesavealpha($image, true);
                if ($this->type == IMAGETYPE_GIF) {
 -                      imageGIF($image);
 +                      imagegif($image);
                }
                else if ($this->type == IMAGETYPE_PNG) {
 -                      imagePNG($image);
 +                      imagepng($image);
                }
                else if (function_exists('imageJPEG')) {
 -                      imageJPEG($image, null, 90);
 +                      imagejpeg($image, null, 90);
                }
                
                $stream = ob_get_contents();