reduce image size using php and shell command, convert and php is very common in ubuntu using them compress/resize the images in folder.

convert.php

<?php
$dir = new DirectoryIterator(dirname(__FILE__));
$count=0;
foreach ($dir as $fileinfo) {
    if (!$fileinfo->isDot()) {
      $output=  shell_exec('convert -resize 50% '.$fileinfo->getFilename().' '.$count.'.jpg');
    }
    $count++;

}
?>