Resize & Crop Images on the Fly?

So, finally I can extract the first thumbnail image from a blog post. The problem is that the image still in their original resolution:

', $str, $output);
    if (!empty($output[1])) {
        echo "";
    } else {
        echo "";
    }
?>

Is it possible to resize and crop the image on the fly just like Picasa does, and also cache the result?

What is Image method used for?

Image::factory($file); // etc...