The Ultimate Smart Image Re-sizing Routine. You provide the original image, and a desired width and/or height. This function will intelligently re-size the original image to fit, centered, within the specified dimensions. Either width or height can be omitted to have the re-size "lock" only on width or height. Fantastic for thumbnail generation.…

smart_img_resize.inc.php

<?

function smart_img_resize($orig, $dest_width=null, $dest_height=null)
{
  $orig_width = imagesx($orig);
  $orig_height = imagesy($orig);
  $vertical_offset = 0;
  $horizontal_offset = 0;
  if($dest_width == null)
  {
    if($dest_height == null)
    {
      die('$dest_width and $dest_height cannot both be null!');
    }
    // height is locked
    $dest_width = $dest_height * $orig_width / $orig_height;
  } else {
    if($dest_height == null)
    {
      // width is locked
      $dest_height = $dest_width * $orig_height / $orig_width;
    } else {
      // both dimensions are locked
      $vertical_offset = $dest_height - ($orig_height * $dest_width) / $orig_width;
      $horizontal_offset = $dest_width - ($dest_height * $orig_width) / $orig_height;
      if($vertical_offset < 0) $vertical_offset = 0;
      if($horizontal_offset < 0) $horizontal_offset = 0;
    }
  }
  $img = imagecreatetruecolor($dest_width, $dest_height);
  imagesavealpha($img, true);
  imagealphablending($img, false);
  $transparent = imagecolorallocatealpha($img, 0, 0, 0, 127);
  imagefill($img, 0, 0, $transparent);
  imagecopyresampled($img, $orig, round($horizontal_offset / 2),
                                  round($vertical_offset / 2),
                                  0,
                                  0,
                                  round($dest_width - $horizontal_offset),
                                  round($dest_height - $vertical_offset),
                                  $orig_width,
                                  $orig_height);
  return $img;
}

?>