/**
* Flip an image horizontally or vertically
*
* @param mixed $image GD resource
* @param string $dir Direction of fliping - x|y|yx|xy
* @return resource
*/
public static function flip($image, $dir)
{
$dir = Helper::direction($dir);
$width = imagesx($image);
$height = imagesy($image);
$newImage = imagecreatetruecolor($width, $height);
Helper::addAlpha($newImage);
if ($dir === 'y') {
for ($y = 0; $y < $height; $y++) {
imagecopy($newImage, $image, 0, $y, 0, $height - $y - 1, $width, 1);
}
} elseif ($dir === 'x') {
for ($x = 0; $x < $width; $x++) {
imagecopy($newImage, $image, $x, 0, $width - $x - 1, 0, 1, $height);
}
} elseif ($dir === 'xy' || $dir === 'yx') {
$newImage = self::flip($image, 'x');
$newImage = self::flip($newImage, 'y');
}
return $newImage;
}