php调整图片宽高实例分享

/** 
 * 改变图片的宽高 
 *  
 * @author flynetcn (2009-12-16) 
 *  
 * @param string $img_src 原图片的存放地址或url  
 * @param string $new_img_path  新图片的存放地址  
 * @param int $new_width  新图片的宽度  
 * @param int $new_height 新图片的高度 
 * @return bool  成功true, 失败false 
 */  
function resize_image($img_src, $new_img_path, $new_width, $new_height)  
{  
    $img_info = @getimagesize($img_src);  
    if (!$img_info || $new_width < 1 || $new_height < 1 || empty($new_img_path)) {  
        return false;  
    }  
    if (strpos($img_info['mime'], 'jpeg') !== false) {  
        $pic_obj = imagecreatefromjpeg($img_src);  
    } else if (strpos($img_info['mime'], 'gif') !== false) {  
        $pic_obj = imagecreatefromgif($img_src);  
    } else if (strpos($img_info['mime'], 'png') !== false) {  
        $pic_obj = imagecreatefrompng($img_src);  
    } else {  
        return false;  
    }  
    $pic_width = imagesx($pic_obj);  
    $pic_height = imagesy($pic_obj);  
    if (function_exists("imagecopyresampled")) {  
        $new_img = imagecreatetruecolor($new_width,$new_height);  
        imagecopyresampled($new_img, $pic_obj, 0, 0, 0, 0, $new_width, $new_height, $pic_width, $pic_height);  
    } else {  
        $new_img = imagecreate($new_width, $new_height);  
        imagecopyresized($new_img, $pic_obj, 0, 0, 0, 0, $new_width, $new_height, $pic_width, $pic_height);  
    }  
    if (preg_match('~.([^.]+)$~', $new_img_path, $match)) {  
        $new_type = strtolower($match[1]);  
        switch ($new_type) {  
            case 'jpg':  
                imagejpeg($new_img, $new_img_path);  
                break;  
            case 'gif':  
                imagegif($new_img, $new_img_path);  
                break;  
            case 'png':  
                imagepng($new_img, $new_img_path);  
                break;  
            default:  
                imagejpeg($new_img, $new_img_path);  
        }  
    } else {  
        imagejpeg($new_img, $new_img_path);  
    }  
    imagedestroy($pic_obj);  
    imagedestroy($new_img);  
    return true;  
}  
  
//test  
$ret = resize_image('http://static.php.net/www.php.net/images/php_snow_2008.gif', 'test.png', '300', '400');  
var_dump($ret);  die;