PHP Imagick getImageChannelDistortions() Function

The Imagick::getImageChannelDistortions() function is an inbuilt function in PHP which is used to compare one or more image channels of an image to a reconstructed image and returns the specified distortion metrics. The difference between getImageChannelDistortion() and getImageChannelDIstortions() is that the latter doesn’t necessarily accepts a channel parameter thus it can take only two parameters also. 

Syntax:

float Imagick::getImageChannelDistortions( Imagick $reference,
             int $metric, int $channel = Imagick::CHANNEL_DEFAULT)

Parameters: This function accepts three parameters as mentioned above and described below:

• $reference: It specifies the Imagick object of image.
• $metric: It specifies one of the metric type constants. List of METRIC constants are given below:
  • imagick::METRIC_UNDEFINED (0)
  • imagick::METRIC_MEANABSOLUTEERROR (1)
  • imagick::METRIC_MEANSQUAREERROR (2)
  • imagick::METRIC_PEAKABSOLUTEERROR (3)
  • imagick::METRIC_PEAKSIGNALTONOISERATIO (4)
  • imagick::METRIC_ROOTMEANSQUAREDERROR (5)
• $channel: It specifies the channel constant that is valid for channel mode. Use bitwise operator to combine more than one channeltype constants. The default value of channel constants is Imagick::CHANNEL_DEFAULT.

Exceptions: This function throws ImagickException on error. 

Return Value: This function returns a double describing channel distortion. Below programs illustrate the Imagick::getImageChannelDistortions() function in PHP: 

Program 1:

php

<?php

// Create two new imagick object
$imagick1 = new Imagick(
'https://media.geeksforgeeks.org/wp-content/uploads/20190823154611/geeksforgeeks24.png');

$imagick2 = new Imagick(
'https://media.geeksforgeeks.org/wp-content/uploads/20190916133223/diamond.png');

// Get the distortion with METRIC constant as imagick::METRIC_MEANABSOLUTEERROR
$distortion = $imagick1->getImageChannelDistortions($imagick2, 1);

echo $distortion;
?>

Output:

23925

Program 2:

php

<?php

// Create two new imagick object
$imagick1 = new Imagick(
'https://media.geeksforgeeks.org/wp-content/uploads/20190823154611/geeksforgeeks24.png');

$imagick2 = new Imagick(
'https://media.geeksforgeeks.org/wp-content/uploads/20190823154611/geeksforgeeks24.png');

// Get the distortion with METRIC constant as imagick::METRIC_MEANABSOLUTEERROR
$distortion = $imagick1->getImageChannelDistortions($imagick2, 1);

echo $distortion;
?>

Output:

0 because both of the images are same.

Program 3:

php

<?php

// Create two new imagick object
$imagick1 = new Imagick(
'https://media.geeksforgeeks.org/wp-content/uploads/20190823154611/geeksforgeeks24.png');

$imagick2 = new Imagick(
'https://media.geeksforgeeks.org/wp-content/uploads/20190916133633/gausian.png');

// Get the distortion with METRIC constant as imagick::METRIC_MEANSQUAREERROR
$distortion = $imagick1->getImageChannelDistortions($imagick2, 2);

echo $distortion;
?>

Output:

0.048318723480804

Reference: https://www.php.net/manual/en/imagick.getimagechanneldistortions.php