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Bug #39366 imagerotate preserve alpha channel only if degree less then 45
Submitted: 2006-11-03 22:16 UTC Modified: 2006-11-04 03:24 UTC
From: ciakana at gmail dot com Assigned: pajoye
Status: Closed Package: GD related
PHP Version: 5.2.0 OS: Windows XP
Private report: No CVE-ID:
 [2006-11-03 22:16 UTC] ciakana at gmail dot com
Description:
------------
If I run the allegated script, where shade.png is a png image with a transparent background (full alpha channel), all works if the degrees are less then 45. If I set the degrees to 300, for example, the background become black.

Reproduce code:
---------------
<?php
$filename="shade.png";
$degrees =300;
header('Content-type: image/png');
$source = imagecreatefrompng($filename);
$rotate = imagerotate($source, $degrees, -1);
imagealphablending($rotate, true);
imagesavealpha($rotate, true);
imagepng($rotate);
?>

Expected result:
----------------
An image with a black bakground

Actual result:
--------------
A rotated copy of the original image with the alpha channel preserved

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 [2006-11-03 22:18 UTC] ciakana at gmail dot com
Description:
------------
If I run the allegated script, where shade.png is a png image with a
transparent background (full alpha channel), all works if the degrees
are less then 45. If I set the degrees to 300, for example, the
background become black.

Reproduce code:
---------------
<?php
$filename="shade.png";
$degrees =300;
header('Content-type: image/png');
$source = imagecreatefrompng($filename);
$rotate = imagerotate($source, $degrees, -1);
imagealphablending($rotate, true);
imagesavealpha($rotate, true);
imagepng($rotate);
?>

Expected result:
----------------
A rotated copy of the original image with the alpha channel preserved

Actual result:
--------------
An image with a black bakground
 [2006-11-04 03:24 UTC] pajoye@php.net
This bug has been fixed in CVS.

Snapshots of the sources are packaged every three hours; this change
will be in the next snapshot. You can grab the snapshot at
http://snaps.php.net/.
 
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