pic.php

<?php
  if(isset($_GET['img'])) $image = getimagesize($_GET['img']);
  else if ($image === false) trigger_error('Error: The URL given is an invalid image.', E_USER_ERROR);
  else trigger_error('Error: The $img variable is no set.', E_USER_ERROR);

  $qlty = isset($_GET['cqlty']) && $_GET['cqlty'] <= 100 ? $_GET['cqlty'] : 80;
  $mime = explode('/', $image['mime']);
  $ext = strtolower($mime[1]);
  list($width, $height) = $image;

  switch($ext){
    case('jpg'): case('jpeg'):
      $buffer = imagecreatefromjpeg($_GET['img']);
    break;
    case('png'):
      $buffer = imagecreatefrompng($_GET['img']);
      $qlty = ($qlty * 0.1 == 10) ? 9 : ceil($qlty * 0.1);
    break;
    case('gif'):
      $buffer = imagecreatefromgif($_GET['img']);
    break;
    default:
      trigger_error('Error: The image format is not supported.', E_USER_ERROR);
    break;
  }

  if(isset($_GET['cwidth'])){
    $new_width = $_GET['cwidth'];
    $new_height = !isset($_GET['cheight']) ? $height * ($new_width/$width) : $_GET['cheight'];
  }
  if(isset($_GET['cheight'])){
    $new_height = $_GET['cheight'];
    $new_width = !isset($_GET['cwidth']) ? $width * ($new_height/$height) : $_GET['cwidth'];
  }
  if(isset($_GET['cut']) && (!isset($_GET['cwidth']) && !isset($_GET['cheight']))){
    $new_width = $new_height = $_GET['cwidth'] = $_GET['cheight'] = min($width, $height);
  }

  if(isset($_GET['cheight']) || isset($_GET['cwidth'])){
    if(isset($_GET['cut'])){
      if(is_numeric($_GET['cut'])) $new_width = $new_height = $_GET['cut']; // If a number is given, make it square
      $w_centre = round($width  / 2);
      $h_centre = round($height / 2);
      $w_half = round($new_width  / 2);
      $h_half = round($new_height / 2);

      $x1 = max(0, ($w_centre - $w_half));
      $y1 = max(0, ($h_centre - $h_half));
      $x2 = min($width,  ($w_centre + $w_half));
      $y2 = min($height, ($h_centre + $h_half));

      $image_resized = imagecreatetruecolor($x2 - $x1, $y2 - $y1);
      if($ext == 'png' || $ext == 'gif') imagealphablending($image_resized, false);
      imagecopy($image_resized, $buffer, 0, 0, $x1, $y1, $width, $height);
    }
    else{
      $image_resized = imagecreatetruecolor($new_width, $new_height);
      imagealphablending($image_resized, false);
      imagecopyresampled($image_resized, $buffer, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
    }
  }
  else $image_resized = $buffer;

  if($ext == 'png' || $ext == 'gif') imagesavealpha($image_resized, true);

  $function = 'image'.$ext;
  header('Content-type: '.$image['mime']);
  if($ext == 'gif') $function($image_resized);
  else $function($image_resized, null, $qlty);

  if(is_resource($buffer))        imagedestroy($buffer);
  if(is_resource($image_resized)) imagedestroy($image_resized);
?>