用php调整图片宽高

<?php
/**
* 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);