对图片进行翻转

<?php
    function turn_y($filename){
        $image_back = imagecreatefromjpeg($filename);
        
        $width = imagesx($image_back);
        $height = imagesy($image_back);
        
        $image_new = imagecreatetruecolor($width,$height);
        
        for($x = 0;$x < $width;$x ++){
            imagecopy($image_new,$image_back,$width - $x - 1,0,$x,0,1,$height);
        }
        
        imagejpeg($image_new,$filename);
        
        imagedestroy($image_back);
        imagedestroy($image_new);
    }
    
    function turn_x($filename){
        $image_back = imagecreatefromjpeg($filename);
        
        $width = imagesx($image_back);
        $height = imagesy($image_back);
        
        $image_new = imagecreatetruecolor($width,$height);
        
        for($y = 0;$y < $height;$y ++){
            imagecopy($image_new,$image_back,0,$height - $y - 1,0,$y,$width,1);
        }
        
        imagejpeg($image_new,$filename);
        
        imagedestroy($image_back);
        imagedestroy($image_new);
    }
    
    turn_x("mm2.jpeg");
?>