Description:
------------
---
From manual page: http://www.php.net/function.imagerotate
---

Linux (RHEL6+PHP5.3.3) works fine.
But with WAMP (Windows7+PHP5.5.12) transparent artifacts appear when using imagerotate.
The artifacts appear only in the transparent area of the image that is rotated.
The transparent aera should only contain pixels with the color code 0X7F000000 but a 'grid'-like pattern of pixels with color code 0x7E000000 appears.
(the alpha channel value should be 127 but some pixels become 126).
In the test script I have replaced the incorrect pixels with a non transparent color to show the pattern.



Test script:
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<?PHP

// create fully transparent canvas
$canvas = imagecreatetruecolor(200,200);
imagesavealpha($canvas, true);
$trans_colour = imagecolorallocatealpha($canvas, 0, 0, 0, 127);
imagefill($canvas, 0, 0, $trans_colour); 
imagesavealpha($canvas, true);

// rotate the canvas 45 degrees
$outputCanvas = imagerotate($canvas, 45, imageColorAllocateAlpha($canvas, 0, 0, 0, 127),0);
imagealphablending($outputCanvas, false);
imagesavealpha($outputCanvas, true);
	
// replace colors not being fully transparent
$blue_color = imageColorAllocateAlpha($outputCanvas, 0, 0, 255, 0);
$width = imagesx($outputCanvas);
$height = imagesy($outputCanvas);
for($y=0;$y<$height;$y++)
{
	for($x=0;$x<$width;$x++)
	{
		$rgb = imagecolorat($outputCanvas, $x, $y);
		if ($rgb != 0x7F000000)
		{
			imagesetpixel($outputCanvas,$x,$y,$blue_color);
		}
	}
}

header("Content-Type: image/png");
imagepng($outputCanvas);

imagedestroy($canvas);
imagedestroy($outputCanvas);
		
?>

Expected result:
----------------
The script rotates a fully transparent image and should show a fully transparent image (shown as a grey image in most browsers).
Pixels that are not fully transparent are colored blue.
No blue pixels should be visible.

Actual result:
--------------
When running the script on windows7 (wamp2.5-PHP5.5.12),
a grid like grey/blue pattern appears which shows that most fully transparent pixels have become not fully transparent during the rotation.
I replaced the pixels that are not correct with a blue color in order to visualize the pattern. 
All pixels should have a alpha value of 127 but somehow most of them become 126.