Imagick::getImageChannelKurtosis

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

Imagick::getImageChannelKurtosisThe getImageChannelKurtosis purpose

Description

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

Get the kurtosis and skewness of a specific channel. This method is available if Imagick has been compiled against ImageMagick version 6.4.9 or newer.

Parameters

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. Defaults to Imagick::CHANNEL_DEFAULT. Refer to this list of channel constants

Return Values

Returns an array with kurtosis and skewness members.

Errors/Exceptions

Throws ImagickException on error.

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User Contributed Notes 1 note

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holdoffhunger at gmail dot com
12 years ago
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
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