Enhances the intensity differences between the lighter and darker elements of the image. Set sharpen to a value other than 0 to increase the image contrast otherwise the contrast is reduced.
function contrastImage($image_path, $contrastType)
{
    $imagick = new \Imagick(realpath($image_path));
    if ($contrastType != 2) {
        $imagick->contrastImage($contrastType);
    }

    header("Content-Type: image/jpg");
    echo $imagick->getImageBlob();
}