PHP loads images in the correct sizes

This code is pretty detailed, but may give you an idea of ​​how to calculate image sizes.

Parameters are the width of your source and the maximum width and height of the maximum size.

function image_resize_dimensions($source_width,$source_height,$thumb_width,$thumb_height)
{
  $source_ratio = $source_width / $source_height;
  $thumb_ratio = $thumb_width / $thumb_height;

  // Ratio is Taller
  if ($thumb_ratio > $source_ratio)
  {
    $result_height = $thumb_height;
    $result_width = $thumb_height * $source_ratio;
  }

  // Ratio is Wider
  elseif ($thumb_ratio < $source_ratio)
  {
    $result_width = $thumb_width;
    $result_height = $thumb_width / $source_ratio;
  }

  // Ratio the Same
  elseif($thumb_ratio == $source_ratio)
  {
    $result_height = $thumb_height;
    $result_width = $thumb_width;
  }

  return array('x'=>$result_width,'y'=>$result_height);

}