Description:
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imagepng creates incorrect sized png file if imagecreatetruecolor parameters are smaller then 26.

e.g. 25 x 25 becomes 31 x 31.

The problems only occurs with imagepng, not with imagejpg nor with imagegif.

Reproduce code:
---------------
<?php
header ("Content-type: image/png");


$im = @imagecreatetruecolor(25, 25) 
		or die("Cannot Initialize new GD image stream");

imagepng($im,null,0);

imagepng($im,'test.png',0);
imagejpeg($im,'test.jpg',100);
imagegif($im,'test.gif');
imagegd2($im,'test.raw');


imagedestroy($im);
?>