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Imagick::getImageChannelKurtosis

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

Imagick::getImageChannelKurtosisThe getImageChannelKurtosis purpose

Descrição

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

Get the kurtosis and skewness of a specific channel. Este método estará disponível se a extensão Imagick tiver sido compilada com a ImageMagick versão 6.4.9 ou superior.

Parâmetros

channel

Fornece qualquer constante de canal que seja válida no modo de canal. Para aplicar a mais de um canal, constantes de canal devem ser combinadas usando operadores bit a bit. O padrão é Imagick::CHANNEL_DEFAULT. Consulte esta lista de constantes de canal

Valor Retornado

Returns an array with kurtosis and skewness members.

Erros/Exceções

Lança uma exceção ImagickException em caso de erro.

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holdoffhunger at gmail dot com
11 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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