<?php

// define the base image dir
$base_img_dir = "./";

// $QUERY_STRING =
//  f(3c9b5fa6bc0fa)  img_file
//  w(123|15%)        width of output
//  h(123|10%)        height of output
//  x(123)            max width of output
//  y(123)            max height of output
//  t(jpg|png)        type of output
//  q(100)            quality of jpeg

// find tags
preg_match_all("/\+*(([a-z])\(([^\)]+)\))\+*/", $QUERY_STRING,
                $matches, PREG_SET_ORDER);

// empty array and set regular expressions for the check
$tags = array();
$check = array( "f" => "[0-9a-zA-Z]{13}",
                "w" => "[0-9]+%?",
                "h" => "[0-9]+%?",
                "x" => "[0-9]+",
                "y" => "[0-9]+",
                "t" => "jpg|png",
                "q" => "1?[0-9]{1,2}" );

// check tags and save correct values in array
for ($i=0; $i<count($matches); $i++) {
    if (isset($check[$matches[$i][2]])) {
        if (preg_match('/^('.$check[$matches[$i][2]].')$/',
               $matches[$i][3])) {
            $tags[$matches[$i][2]] = $matches[$i][3];
        }
    }
}

function notfound() {
    header("HTTP/1.0 404 Not Found");
    exit;
}

// check that filename is given
if (!isset($tags["f"])) {
    notfound();
}

// check if file exists
if (!file_exists($base_img_dir.$tags["f"])) {
    notfound();
}

// retrieve file info
$imginfo = getimagesize($base_img_dir.$tags["f"]);

// load image
switch ($imginfo[2]) { 
    case 2:     // jpg
        $img_in = imagecreatefromjpeg($base_img_dir.$tags["f"]) or notfound();
        if (!isset($tags["t"])) {
            $tags["t"] = "jpg";
        }
        break;
    case 3:     // png
        $img_in = imagecreatefrompng($base_img_dir.$tags["f"]) or notfound();
        if (!isset($tags["t"])) {
            $tags["t"] = "png";
        }
        break;
    default:
        notfound();
}

// check for maximum width and height
if (isset($tags["x"])) {
    if ($tags["x"] < imagesx($img_in)) {
        $tags["w"] = $tags["x"];
    }
}
if (isset($tags["y"])) {
    if ($tags["y"] < imagesy($img_in)) {
        $tags["h"] = $tags["y"];
    }
}

// check for need to resize
if (isset($tags["h"]) or isset($tags["w"])) {
    // convert relative to absolute
    if (isset($tags["w"])) {
        if (strstr($tags["w"], "%")) {
            $tags["w"] = (intval(substr($tags["w"], 0, -1)) / 100) *
                          $imginfo[0];
        }
    }
    if (isset($tags["h"])) {
        if (strstr($tags["h"], "%")) {
            $tags["h"] = (intval(substr($tags["h"], 0, -1)) / 100) *
                          $imginfo[1];
        }
    }

    // resize
    if (isset($tags["w"]) and isset($tags["h"])) {
        $out_w = $tags["w"];
        $out_h = $tags["h"];
    } elseif (isset($tags["w"]) and !isset($tags["h"])) {
        $out_w = $tags["w"];
        $out_h = $imginfo[1] * ($tags["w"] / $imginfo[0]);
    } elseif (!isset($tags["w"]) and isset($tags["h"])) {
        $out_w = $imginfo[0] * ($tags["h"] / $imginfo[1]);
        $out_h = $tags["h"];
    } else {
        $out_w = $tags["w"];
        $out_h = $tags["h"];
    }
    
    // new image in $img_out
    $img_out = imagecreate($out_w, $out_h);
    imagecopyresized($img_out, $img_in, 0, 0, 0, 0, imagesx($img_out),
               imagesy($img_out), imagesx($img_in), imagesy($img_in));
} else {
    // no resize needed
    $img_out = $img_in;
}

// check for a given jpeg-quality, otherwise set to default
if (!isset($tags["q"])) {
    $tags["q"] = 75;
}

// returning the image
switch ($tags["t"]) {
    case "jpg":
        header("Content-type: image/jpeg");
        imagejpeg($img_out, "", $tags["q"]);
        exit;
    case "png":
        header("Content-type: image/png");
        imagepng($img_out);
        exit;
   default:
        notfound();
}

?>