protected function grayscaleEntropy(\Imagick $image)
    {
        // The histogram consists of a list of 0-254 and the number of pixels that has that value
        $histogram = $image->getImageHistogram();

        return $this->getEntropy($histogram, $this->area($image));
    }
protected function grayscaleEntropy(\Imagick $image)
    {
        // The histogram consists of a list of 0-254 and the number of pixels that has that value
        $histogram = $image->getImageHistogram();

        return $this->getEntropy($histogram, $this->area($image));
    }
protected function grayscaleEntropy ( \ Imagick $ image ) { // The histogram consists of a list of 0-254 and the number of pixels that has that value $ histogram = $ image -> getImageHistogram ( ) ; return $ this -> getEntropy ( $ histogram , $ this -> area ( $ image ) ) ; }
Calculate the entropy for this image.

A higher value of entropy means more noise / liveliness / color / business

@param  \Imagick $image
@return float

@see http://brainacle.com/calculating-image-entropy-with-python-how-and-why.html
@see http://www.mathworks.com/help/toolbox/images/ref/entropy.html
Calculate the entropy for this image .