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Imagick::getImageChannelKurtosis

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Imagick::getImageChannelKurtosisThe getImageChannelKurtosis purpose

Descrição

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

Get the kurtosis and skewness of a specific channel. Este método está disponível se o PHP foi compilado com o ImageMagick versão 6.4.9 ou superior.

Parâmetros

channel

Informa qualquer constante de canal válida no modo do canal. Para mais de um canal, combine as constantes de canal utilizando operações bitwise. O padrão é Imagick::CHANNEL_DEFAULT. Veja nessa lista de constantes de canal

Valor Retornado

Returns an array with kurtosis and skewness members.

Erros

Lança ImagickException em caso de erro.

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User Contributed Notes 1 note

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holdoffhunger at gmail dot com
4 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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