php 根据url自动生成缩略图

原理：设置apache rewrite ，当图片不存在时，调用php创建图片。
例如
原图路径为：http://localhost/upload/news/2013/07/21/1.jpg
缩略图路径为：http://localhost/supload/news/2013/07/21/1.jpg

当访问 http://localhost/supload/news/2013/07/21/1.jpg 时，如图片存在，则显示图片。否则，调用createthumb.php生成图片。

目录结构如下：
www/PicThumb.class.php
www/ThumbConfig.php
www/upload/news/2013/07/21/1.jpg
www/upload/article/2013/07/21/2.jpg
www/supload/.htaccess
www/supload/watermark.png
www/supload/createthumb.php

http://localhost/ 指向 www目录

PicThumb.class.php 用法请查看这里

需要开启apache rewrite

sudo a2enmod rewrite

.htaccess

<IfModule mod_rewrite.c>
RewriteEngine On

# '-s' (is regular file, with size)
# '-l' (is symbolic link)
# '-d' (is directory)
# 'ornext|OR' (or next condition)
# 'nocase|NC' (no case)
# 'last|L' (last rule)

RewriteCond %{REQUEST_FILENAME} -s [OR]
RewriteCond %{REQUEST_FILENAME} -l [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^.*$ - [NC,L]
RewriteRule ^.*$ createthumb.php?path=%{REQUEST_URI} [NC,L]

</IfModule>

createthumb.php

<?php
define('WWW_PATH', dirname(dirname(__FILE__))); // 站点www目录

require(WWW_PATH.'/PicThumb.class.php'); // include PicThumb.class.php
require(WWW_PATH.'/ThumbConfig.php');    // include ThumbConfig.php

$logfile = WWW_PATH.'/createthumb.log';  // 日志文件
$source_path = WWW_PATH.'/upload/';      // 原路径
$dest_path = WWW_PATH.'/supload/';       // 目标路径

$path = isset($_GET['path'])? $_GET['path'] : '';  // 访问的图片URL

// 检查path
if(!$path){
    exit();
}

// 获取图片URI
$relative_url = str_replace($dest_path, '', WWW_PATH.$path);

// 获取type
$type = substr($relative_url, 0, strpos($relative_url, '/'));

// 获取config
$config = isset($thumb_config[$type])? $thumb_config[$type] : '';

// 检查config
if(!$config || !isset($config['fromdir'])){
    exit();
}

// 原图文件
$source = str_replace('/'.$type.'/', '/'.$config['fromdir'].'/', $source_path.$relative_url);

// 目标文件 
$dest = $dest_path.$relative_url;

// 创建缩略图
$obj = new PicThumb($logfile);
$obj->set_config($config);
if($obj->create_thumb($source, $dest)){
    ob_clean();
    header('content-type:'.mime_content_type($dest));
    exit(file_get_contents($dest));
}

?>

ThumbConfig.php

<?php

$thumb_config = array(

    'news' => array(
        'fromdir' => 'news', // 来源目录
        'type' => 'fit',
        'width' => 100,
        'height' => 100,
        'bgcolor' => '#FF0000'
    ),

    'news_1' => array(
        'fromdir' => 'news',
        'type' => 'fit',
        'width' => 200,
        'height' => 200,
        'bgcolor' => '#FFFF00'
    ),

    'article' => array(
        'fromdir' => 'article',
        'type' => 'crop',
        'width' => 250,
        'height' => 250,
        'watermark' => WWW_PATH.'/supload/watermark.png'
    )

);

?>

访问这三个路径后会按config自动生成缩略图http://localhost/supload/news/2013/07/21/1.jpghttp://localhost/supload/news_1/2013/07/21/1.jpghttp://localhost/supload/article/2013/07/21/2.jpg

源码下载地址：点击下载