This problem was fixed today by developers in code repository. You can patch your file with fixed code or you can download new version with some new stuff from svn
here is fixed code
$im_p = imagecreatetruecolor($dest_width, $dest_height);
$color = imagecolortransparent($im_p, imagecolorallocatealpha($im_p, 255, 255, 255, 127));
imagefill($im_p, 0, 0, $color);
I just tested it, work like charm
Thanks for update.