index.php[主程序]

<?php
error_reporting(E_ERROR);
require_once '../include/common.php';
require_once 'lib/imgdata.php';
require_once 'lib/functions.php';

$karnc=new imgdata;if($_GET['a']=='local'){
    /* 列出指定目录下的图片 */
    $CONFIG=array(
        'imageManagerAllowFiles'=>array(".png", ".jpg", ".jpeg", ".gif", ".bmp"),/* 列出的文件类型 */
        'imageManagerListPath'=>"/background/upload/",/* 列出的文件地址（重要，可根据需求自行修改） */
    );

    $host='http://'.$_SERVER['HTTP_HOST'];

    $allowFiles = $CONFIG['imageManagerAllowFiles'];
    $path = $CONFIG['imageManagerListPath'];

    $allowFiles = substr(str_replace(".", "|", join("", $allowFiles)), 1);

    /* 获取文件列表 */
    $path = $_SERVER['DOCUMENT_ROOT'] . (substr($path, 0, 1) == "/" ? "":"/") . $path;
    $files = getfiles($path,$allowFiles);
    if (!count($path) || empty($files)) {
        $imgFile='http://api.karnc.com/background/404.jpg';
        $karnc->getdir($imgFile);
        $karnc->img2data();
        $karnc->data2img();die;
    }

    /* 获取指定范围的列表 */
    $len = count($files);
    for ($i = 0, $list = array(); $i < $len; $i++){
        $list[] = $files[$i];
    }

    $rand=array_rand($list,1);

    $img=$list[$rand];

    $imgUrl=$host.$img;

    $imgFile=$_SERVER['DOCUMENT_ROOT'] . (substr($list[$rand], 0, 1) == "/" ? "":"/").$img;}else{
    //这里是从数据库中取相应图片
    $img=$db_pdo->getOne("select `ming` from sd_file where quality = 1 ORDER BY RAND() limit 1");
    $host='https://static.karnc.com/';
    $imgFile=$imgUrl=$host.$img['ming'];}$refer=  $_SERVER['HTTP_REFERER']; //前一URL//存在前一URLif($refer){
    if(!checkReferer()){
        $imgFile='http://api.karnc.com/background/404.jpg';
    }
    $karnc->getdir($imgFile);
    $karnc->img2data();
    $karnc->data2img();die;}else{
    //直接访问
    echo "<script>location.href='".$imgUrl."'</script>";die;
}
?>

imgdata.php(浏览器输出图片类)

<?php
class imgdata{
    public $imgsrc;
    public $imgdata;
    public $imgform;
    public function getdir($source){
        $this->imgsrc  = $source;
    }
    public function img2data(){
        $this->_imgfrom($this->imgsrc);
        return $this->imgdata=fopen($this->imgsrc,'rb');
    }
    public function data2img(){
        header("content-type:$this->imgform");
        return fpassthru($this->imgdata);
    }
    public function _imgfrom($imgsrc){
        $info=getimagesize($imgsrc);
        return $this->imgform = $info['mime'];
    }
}
?>

function.php(公共函数)

<?php

/**
 * 遍历获取目录下的指定类型的文件
 * @param $path
 * @param array $files
 * @return array
 */function getfiles($path,$allowFiles,&$files = array())
 {
    if (!is_dir($path)) return null;
    if(substr($path, strlen($path) - 1) != '/') $path .= '/';
    $handle = opendir($path);
    while (false !== ($file = readdir($handle))) {
        if ($file != '.' && $file != '..') {
            $path2 = $path . $file;
            if (is_dir($path2)) {
                getfiles($path2, $allowFiles, $files);
            } else {
                if (preg_match("/\.(".$allowFiles.")$/i", $file)) {
                    $files[] =substr($path2, strlen($_SERVER['DOCUMENT_ROOT']));
                }
            }
        }
    }
    return $files;}/**
 * 域名白名单校验
 * @param $domain_list(白名单)
 * @return true/false
 */
 function checkReferer($domain_list=array('karnc.com','www.karnc.com')){
    $status=false;
    $refer=  $_SERVER['HTTP_REFERER']; //前一URL
    if($refer){
        $referhost=parse_url($refer);
        $host=strtolower($referhost['host']);//来源地址主域名
        if($host==$_SERVER['HTTP_HOST'] || in_array($host,$domain_list)){
            $status=true;
        }
    }
    return $status;
}
?>

可让php直接在浏览器中输出图片，支持本地文件也支持图片链接。