使用方法示例：
设定宽度，等比例缩放
复制代码 代码如下:
<?php
   include('SimpleImage.php');
   $image = new SimpleImage();
   $image->load('picture.jpg');
   $image->resizeToWidth(250);
   $image->save('picture2.jpg');?>
设定高度，等比例缩放
复制代码 代码如下:
<?php
   include('SimpleImage.php');
   $image = new SimpleImage();
   $image->load('picture.jpg');
   $image->resizeToHeight(500);
   $image->save('picture2.jpg');
   $image->resizeToHeight(200);
   $image->save('picture3.jpg');?>
按比例，缩放至50%
复制代码 代码如下:
<?php
   include('SimpleImage.php');
   $image = new SimpleImage();
   $image->load('picture.jpg');
   $image->scale(50);
   $image->save('picture2.jpg');?>
缩放后直接输出到屏幕
复制代码 代码如下:
<?php
   header('Content-Type: image/jpeg');
   include('SimpleImage.php');
   $image = new SimpleImage();
   $image->load('picture.jpg');
   $image->resizeToWidth(150);
   $image->output();?>

使用例子：
复制代码 代码如下:
<?php
include("SimpleImage.php");//图片处理类在下面

$url="http://f3.v.veimg.cn/meadincms/1/2013/0703/20130703100937552.jpg";
$picfile = down($url);//下载图片（下载图片的路径可以处理完成后清空，这里未进行处理）
$res = new SimpleImage();//图片处理实例
$res = $res->load($picfile);
$tmpfile = tempfile().'.jpg';//创建一个路径文件用来保存图片
$width = '30';//设定图片的宽度
$res->resizeToWidth($width);
$res->save($tmpfile);//把处理后的图片保存（无.jpg后缀）
//这里总共产生了3个文件，一个是下载的图片文件，一个是临时文件，最后一个是处理的图片文件。需要优化清理掉前两个文件。

function down($url)
{
        $http = array();
        $header = "http://f3.v.veimg.cn";
        if ($header) {
            $http['header'] = $header;
        }

        $http['timeout'] = 50;

        $ctx = stream_context_create(array(
            'http' => $http,
        ));
        $content = @file_get_contents($url, 0, $ctx);
        sleep(1);

        if (!$content) {
            return false;
        }

        $tmpfile = tempfile();

        file_put_contents($tmpfile, $content);

        return $tmpfile;
}

function tempfile()
{
        $path = dirname(__FILE__);
        $path .= '/spider/' . date('Ymd') . '/'.date('His').'-' . (int)(time() / 300);

        if (!file_exists($path)) {
            mkdir($path, 0777, true);
        }

        do {
            $file = $path . '/' . dechex(mt_rand());
        }
        while (file_exists($file));

        touch($file);

        return $file;
}

图片处理类源码（官网地址：http://www.white-hat-web-design.co.uk/blog/resizing-images-with-php/）：
复制代码 代码如下:
<?php

/*
* File: SimpleImage.php
* Author: Simon Jarvis
* Copyright: 2006 Simon Jarvis
* Date: 08/11/06
* Link: http://www.white-hat-web-design.co.uk/articles/php-image-resizing.php
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details:
* http://www.gnu.org/licenses/gpl.html
*
*/

class SimpleImage {

    var $image;
    var $image_type;

    function load($filename) {

        $image_info = getimagesize($filename);
        $this->image_type = $image_info[2];
        if( $this->image_type == IMAGETYPE_JPEG ) {

            $this->image = @imagecreatefromjpeg($filename);
        } elseif( $this->image_type == IMAGETYPE_GIF ) {

            $this->image = @imagecreatefromgif($filename);
        } elseif( $this->image_type == IMAGETYPE_PNG ) {

            $this->image = @imagecreatefrompng($filename);
        }

        if (!$this->image) {
            return false;
        }

        return $this;
    }

    function save($filename, $image_type=IMAGETYPE_JPEG, $compression=75, $permissions=null) {

        if( $image_type == IMAGETYPE_JPEG ) {
            imagejpeg($this->image,$filename,$compression);
        } elseif( $image_type == IMAGETYPE_GIF ) {

            imagegif($this->image,$filename);
        } elseif( $image_type == IMAGETYPE_PNG ) {

            imagepng($this->image,$filename);
        }
        if( $permissions != null) {

            chmod($filename,$permissions);
        }
    }
    function output($image_type=IMAGETYPE_JPEG) {

        if( $image_type == IMAGETYPE_JPEG ) {
            imagejpeg($this->image);
        } elseif( $image_type == IMAGETYPE_GIF ) {

            imagegif($this->image);
        } elseif( $image_type == IMAGETYPE_PNG ) {

            imagepng($this->image);
        }
    }
    function getWidth() {

        return imagesx($this->image);
    }
    function getHeight() {

        return imagesy($this->image);
    }
    function resizeToHeight($height) {

        $ratio = $height / $this->getHeight();
        $width = $this->getWidth() * $ratio;
        $this->resize($width,$height);
    }

    function resizeToWidth($width) {
        if ($this->getWidth() < $width) {
            $width = $this->getWidth();
        }
        $ratio = $width / $this->getWidth();
        $height = $this->getheight() * $ratio;
        $this->resize($width,$height);
    }

    function scale($scale) {
        $width = $this->getWidth() * $scale/100;
        $height = $this->getheight() * $scale/100;
        $this->resize($width,$height);
    }

    function resize($width,$height) {
        $new_image = imagecreatetruecolor($width, $height);
        imagecopyresampled($new_image, $this->image, 0, 0, 0, 0, $width, $height, $this->getWidth(), $this->getHeight());
        $this->image = $new_image;
    }

 
    function resize2($width,$height) {
        $new_image = imagecreatetruecolor($width, $height);
        if( $this->image_type == IMAGETYPE_GIF || $this->image_type == IMAGETYPE_PNG ) {
            $current_transparent = imagecolortransparent($this->image);
            if($current_transparent != -1) {
                $transparent_color = imagecolorsforindex($this->image, $current_transparent);
                $current_transparent = imagecolorallocate($new_image, $transparent_color['red'], $transparent_color['green'], $transparent_color['blue']);
                imagefill($new_image, 0, 0, $current_transparent);
                imagecolortransparent($new_image, $current_transparent);
            } elseif( $this->image_type == IMAGETYPE_PNG) {
                imagealphablending($new_image, false);
                $color = imagecolorallocatealpha($new_image, 0, 0, 0, 127);
                imagefill($new_image, 0, 0, $color);
                imagesavealpha($new_image, true);
            }
        }
        imagecopyresampled($new_image, $this->image, 0, 0, 0, 0, $width, $height, $this->getWidth(), $this->getHeight());
        $this->image = $new_image;  
    }

}