Simulates a charcoal drawing.
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Radius
Sigma
Image
Simulates a charcoal drawing.
Parameters
radiusfloatThe radius of the Gaussian, in pixels, not counting the center pixel
sigmafloatThe standard deviation of the Gaussian, in pixels
function charcoalImage($imagePath, $radius, $sigma)
{
    $imagick = new \Imagick(realpath($imagePath));
    $imagick->charcoalImage($radius, $sigma);
    header("Content-Type: image/jpg");
    echo $imagick->getImageBlob();
}