$transparent_color = imagecolorsforindex($image_src, $transparent_idx);
$transparent_idx = imagecolorallocate($image_dest, $transparent_color['red'], $transparent_color['green'], $transparent_color['blue']);
imagefill($image_dest, 0, 0, $transparent_idx);
imagecolortransparent($image_dest, $transparent_idx);
$transparent_color = imagecolorsforindex($image_src, $transparent_idx);
$transparent_idx = imagecolorallocate($image_dest, $transparent_color['red'], $transparent_color['green'], $transparent_color['blue']);
imagefill($image_dest, 0, 0, $transparent_idx);
imagecolortransparent($image_dest, $transparent_idx);