Random image script I wrote years ago. GISTed because someone asked for it.

random_img.php

<?php
/* Random Image Generator
* Base code & Inspiration by : Maciek "Tularis" Sokolewicz
* ReWritten and enhanced by : Filip H.F. "FiXato" Slagter
* Contact : fixato@gmail.com
* Uses privately adapted version of Directory Listing Script found at : http://php.net/readdir (created by php@silisoftware.com on 31-Jan-2003 04:16)
*/

if(!function_exists('image_type_to_mime_type')) { //check if function exists...
//Alternate version of Image_Type_To_Mime_Type()-function, if that function is absent
//By Filip H.F. "FiXato" Slagter
        function image_type_to_mime_type($imageType)    {
        $return = FALSE;
        switch($imageType)      {
                case 1:
                        $return = 'image/gif';
                break;

                case 2:
                        $return = 'image/jpeg';
                break;

                case 3:
                        $return = 'image/png';
                break;

                case 4:
                        $return = 'application/x-shockwave-flash';
                break;

                case 5:
                        $return = 'image/psd';
                break;

                case 6:
                        $return = 'image/bmp';
                break;

                case 7:
                        $return = 'image/tiff';
                break;

                case 8:
                        $return = 'image/TIFF';
                break;

                case 9:
                        $return = 'image/jpeg';
                break;

                case 10:
                        $return = 'application/octet-stream';
                break;

                case 11:
                        $return = 'application/octet-stream';
                break;

                case 12:
                        $return = 'application/octet-stream';
                break;

                case 13:
                        $return = 'application/x-shockwave-flash';
                break;

                case 14:
                        $return = 'image/iff';
                break;

                case 15:
                        $return = 'application/octet-stream';
                break;
        }
        return $return;
        }
}


function setImageSize($filename, $width='', $height='') {
        //Function to resize Images, while maintaining a reasonable aspect-ratio
        //Created by Filip H.F. "FiXato" Slagter
        if(file_exists($filename))      {
                $imageInfo = getImageSize($filename);
                $imageSizes['width'] = $imageInfo[0];
                $imageSizes['height'] = $imageInfo[1];
                if($width !='' && $height !='') {
                        $imageSizes = resize($width, $height, $imageSizes);
                }
                if(isset($imageInfo['mime']))   {
                        $mime = $imageInfo['mime'];
                }
                else    {
                        $mime = FALSE;
                }
                if(isset($imageInfo['channels']))       {
                        $channels = $imageInfo['channels'];
                }
                else    {
                        $channels = 'undefined';
                }
                if(isset($imageInfo['bits']))   {
                        $bits = $imageInfo['bits'];
                }
                else    {
                        $bits = 'undefined';
                }
                $fileSize = filesize($filename);
                $exifOutput = '';
                /* Commented out because of invalid exif-function
                if(function_exists('exif_read_data'))   {
                        $exif = @exif_read_data ('$filename',0,true);
                        foreach($exif as $key=>$section) {
                                foreach($section as $name=>$val) {
                                        $exifOutput .= "$key.$name: $val<br />\n";
                                }
                        }
                }
                */
                $ext = $imageInfo[2];

                if($ext != '' && function_exists('image_type_to_mime_type'))    {
                        $altContentType = image_type_to_mime_type($ext);
                }
                else    {
                        $altContentType = 'application/octet-stream';
                }

                $returnArray = array('filename' => $filename,
                'origWidth' => $imageInfo[0],
                'origHeight' => $imageInfo[1],
                'height' => ceil($imageSizes['height']),
                'width' => ceil($imageSizes['width']),
                'mime' => $mime,
                'ext' => $ext,
                'altContentType' => $altContentType,
                'altMime' => $altContentType,
                'channels' => $channels,
                'bits' => $bits,
                'exif' => $exifOutput,
                'fileSize' => $fileSize);
                return $returnArray;
        }
        else    {
                return FALSE;
        }
}

function random($dirArray = array('.') )        {
        //init
        for($i = 0; $i < count($dirArray); $i++)        {
                $dirsToScan[] = realpath($dirArray[$i]);
        }
        $array  = array();
        $num    = 0;
        $temp   = array();
        mt_srand((double)microtime()*1000000); //init random generator
        $file   = '';
        $dirKey = '';
        $startingDir = '';
        $allowedExts = array('jpg', 'jpe', 'jpeg', 'gif', 'png', 'bmp');
        $dirsScanned = array();
        while (count($dirsToScan) > 0) {
          foreach ($dirsToScan as $dirKey => $startingDir) {
            if ($dir = opendir($startingDir)) {
              while (($file = readdir($dir)) !== false) {
                $ext = strtolower(substr(strrchr($file,"."),1));
                if (($file != '.') && ($file != '..') && in_array($ext,$allowedExts) && $file != '') { //ignore current Dir, upper Dir, ignore empty filesnames and check for FileExtenion
                  $realPathName = realpath($startingDir.'/'.$file);
                  if (is_dir($realPathName)) {
                    if (!in_array($realPathName, $dirsScanned) && !in_array($realPathName, $dirsToScan)) {
                      $dirsToScan[] = $realPathName;
                    }
                  } elseif (is_file($realPathName)) {
                    $filesInDir[] = $realPathName;
                    $filesInDir2[] = $file;
                  }
                }
              }
              closedir($dir);
            }
            $dirsScanned[] = $startingDir;
            unset($dirsToScan[$dirKey]);
          }
        }


        $count = count($filesInDir);
        $num = mt_rand(0, ($count-1));

        if($count > 0){
                //$size = getimagesize($filesInDir[$num]);
                $imgInfo = setImageSize($filesInDir[$num]);
                $stream = fopen($filesInDir[$num], "rb");
                if($imgInfo && $stream){
                        header('Cache-Control: no-cache, must-revalidate');
                        header('Pragma: no-cache');
                        header('Expires: 0');
                        header('Content-Disposition: inline; filename="'.$filesInDir2[$num].'"');
                        header('Content-Description: Random '.$imgInfo['channels'].' Channels, '.$imgInfo['bits'].'bits '.$imgInfo['ext'].'-Image File');
                        header('Content-Length: '.$imgInfo['fileSize']);
                        header('Content-Type: '.$imgInfo['altMime']);
                        fpassthru($stream);
                        header ('Connection: close');
                        exit();
                }
                }else{
                echo 'no images';
        }
}
random(array('.'));
?>