Blurs an image. We convolve the image with a Gaussian operator of the given radius and standard deviation (sigma). For reasonable results, the radius should be larger than sigma. Use a radius of 0 and selects a suitable radius for you.
function gaussianBlurImage($image_path, $radius, $sigma, $channel)
{
    $imagick = new \Imagick(realpath($image_path));
    $imagick->gaussianBlurImage($radius, $sigma, $channel);
    header("Content-Type: image/jpg");
    echo $imagick->getImageBlob();
}