(PECL imagick 2, PECL imagick 3)
Imagick::charcoalImage — Simulates a charcoal drawing
public Imagick::charcoalImage ( float $radius , float $sigma ) : bool
Simulates a charcoal drawing.
radius
The radius of the Gaussian, in pixels, not counting the center pixel
sigma
The standard deviation of the Gaussian, in pixels
 Returns true on success. 
Example #1 Imagick::charcoalImage()
<?php
function charcoalImage($imagePath, $radius, $sigma) {
    $imagick = new \Imagick(realpath($imagePath));
    $imagick->charcoalImage($radius, $sigma);
    header("Content-Type: image/jpg");
    echo $imagick->getImageBlob();
}
?> 
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    https://www.php.net/manual/en/imagick.charcoalimage.php