Imagick setSamplingFactors in php

Question

I am using Imagick in PHP to create an image with the property "chroma subsampling" to 4:2:2 (2x1,1x1,1x1)

I use this code:

$image = new Imagick('test.jpg');

$factors = array("2,1,1");

$image->setSamplingFactors($factors);

$image->writeImage('test2.jpg');

$image->destroy();

but the result is:

jpeg:sampling-factor: 2x2,1x1,1x1

To see the image's properties; I use:

$image = new Imagick(test2.jpg');
$identify = $image->identifyImage(TRUE);
$data = $identify['rawOutput'];

I want to set:

jpeg:sampling-factor: 2x1,1x1,1x1

Thanks in advance for your help and time

Answer 1

I found one solution using shell_exec,

<?php

$path = "e3.jpg";
$path2 = "e3.jpg";
$arr = array("-sampling-factor 4:2:2");

$properties = "";
foreach ($arr as $property) {
    $properties .= $property." ";
}

$cmd = "convert ".$path." ".$properties." ".$path2;

shell_exec($cmd);

?>

I hope to find the right solution using only imagick methods.