resize.php

function resizeImage($file,$scale="",$width="",$height="")
 {
        // If they wish to scale the image.
        if (isset($scale))
        {
               // Create our image object from the image.
               $fullImage = imagecreatefromjpeg($file);
               // Get the image size, used in calculations later.
               $fullSize = getimagesize($file);
               // If there is NOT a thumbnail for this image, make one.
               if (!file_exists("tn_".$file))
               {
                      // Create our thumbnail size, so we can resize to this, and save it.
                      $tnImage = imagecreatetruecolor($fullSize[0]/$scale, $fullSize[1]/$scale);
                      // Resize the image.
                      imagecopyresampled($tnImage,$fullImage,0,0,0,0,$fullSize[0]/$scale,$fullSize[1]/$scale,$fullSize[0],$fullSize[1]);
                      // Create a new image thumbnail.
                      imagejpeg($tnImage, "tn_".$file);
                      
                      // Clean Up.
                      imagedestroy($fullImage);
                      imagedestroy($tnImage);
                      // Return our new image.
                      return "tn_".$file;
               }
               // If there is a thumbnail file, lets just load it.   
               else
                      return "tn_".$file;
        }
        // If they want to force whatever size they want.
        elseif (isset($width) && isset($height))
        {
               return "tn_".$file;
        }
        else
        {
               return false;
        }
 }