Imagick::getImageChannelKurtosis

(PECL imagick 2 >= 2.3.0, PECL imagick 3)

Imagick::getImageChannelKurtosis — The getImageChannelKurtosis purpose

说明

public Imagick::getImageChannelKurtosis ( int $channel = Imagick::CHANNEL_DEFAULT ) : array

Get the kurtosis and skewness of a specific channel. 此方法在Imagick基于ImageMagick 6.4.9以上版本编译时可用。

参数

channel: Provide any channel constant that is valid for your channel mode. To apply to more than one channel, combine channel constants using bitwise operators. 缺省为Imagick::CHANNEL_DEFAULT. 参考此通道常数列表

返回值

Returns an array with kurtosis and skewness members.

错误／异常

错误时抛出 ImagickException。

User Contributed Notes

holdoffhunger at gmail dot com 15-May-2012 11:52


The getImageChannelKurtosis function accepts as a parameter any of the ImageMagick channel constants and returns an array containing elements with the two element values of 'kurtosis' and 'skewness.'



For the inputted color values, you have the ImageMagick channel constant values that look like imagick::CHANNEL_UNDEFINED, with "_VALUE" values of: undefined, red, gray, cyan, green, magenta, blue, yellow, alpha, opacity, matte, black, index, all, and default.  This is for measuring the particular channel for these colors of their own associated colorspaces.



According to Wikipedia, the Kurtosis is "any measure of the 'peakedness' of the probability distribution of a real-valued random variable" and Skewness (its opposite) is "a measure of the asymmetry of the probability distribution of a real-valued random variable."  The more colors vary from the inputted channel constant, you'll be more likely to get a skewness close to zero, and you'll get the opposite behavior from checking the kurtosis value, which makes sense, since skewness and kurtosis are considered mathematical antonyms.



Some sample code :



<?php



            // Author: holdoffhunger@gmail.com

    

        // Imagick Type

        // ---------------------------------------------



    $imagick_type = new Imagick();

    

        // Open File

        // ---------------------------------------------

        

    $file_to_grab = "image_workshop_directory/test.bmp";

    

    $file_handle_for_viewing_image_file = fopen($file_to_grab, 'a+');

    

        // Grab File

        // ---------------------------------------------



    $imagick_type->readImageFile($file_handle_for_viewing_image_file);

    

        // Get Quantum Range

        // ---------------------------------------------

        

    $imagick_type_channel_kurtosis_red = $imagick_type->getImageChannelKurtosis(imagick::CHANNEL_RED);

    

        // Print Results

        // ---------------------------------------------



    print("<pre>");

    print_r($imagick_type_channel_kurtosis_red);

    print("</pre>");



?>



The results for performing this function upon a photo of the ocean...



ImageMagick - Channel Kurtosis

  Channel - Undefined :



Kurtosis : 0

Skewness : 0



  Channel - Red :



Kurtosis : 0.920611158888

Skewness : 1.52701528976



  Channel - Gray :



Kurtosis : 0.920611158888

Skewness : 1.52701528976



  Channel - Cyan :



Kurtosis : 0.920611158888

Skewness : 1.52701528976



  Channel - Green :



Kurtosis : -0.286520845928

Skewness : 1.05203603783



  Channel - Magenta :



Kurtosis : -0.286520845928

Skewness : 1.05203603783



  Channel - Blue :



Kurtosis : -0.849997917796

Skewness : 0.807852655795



  Channel - Yellow :



Kurtosis : -0.849997917796

Skewness : 0.807852655795



  Channel - Alpha :



Kurtosis : 0

Skewness : 0



  Channel - Opacity :



Kurtosis : 0

Skewness : 0



  Channel - Matte :



Kurtosis : 0

Skewness : 0



  Channel - Black :



Kurtosis : 0

Skewness : 0



  Channel - Index :



Kurtosis : 0

Skewness : 0



  Channel - All :



Kurtosis : 0.509521246195

Skewness : 1.33491479552



  Channel - Default :



Kurtosis : -0.349955122843

Skewness : 1.00561407035