Convert RGB to CMYK in PHP with Imagick

rgb2cmyk.php

<?php

$iccProfile = '../path_to_icc/Profile.icc';
$image = new Imagick();
$image->clear();
$image->readImage($imagePath);
if ($image->getImageColorspace() == Imagick::COLORSPACE_CMYK) { 
    return;
}
$iccCmyk = file_get_contents($iccProfile);
$image->profileImage('icc', $iccCmyk);
unset($iccCmyk);
$image->transformImageColorspace(Imagick::COLORSPACE_CMYK);
$image->writeImage($newImagePath);

Hey,

really glad it helped you!

As for the suggestions / questions:

• what is the point of lines 9 and 11, and of the var $iccCmyk ?

You're right, I misstyped, the '../path_to_icc/Profile.icc' should be the $iccCmyk variable instead (will fix it in the code).

• the profile name argument (first of method $image->profileImage($name, $pathToProfile) must be 'cmyk', not 'icc'. An error occurs if so...

Interesting, my code contains the icc profile parameter and does not throw an error.
Might be due to different Imagick versions, or maybe a difference in files, not too sure. For reference my Imagick is currently at:

"versionNumber" => 1673
"versionString" => "ImageMagick 6.8.9-9 Q16 x86_64 2019-11-12 http://www.imagemagick.org"

• If this transformation concerns web images, the Profile.icc must be >this file< - provided by Adobe for Web images

I actually pass different ICC Profile files based on what i'm converting the CMYK for, currently one is similar to this one: CoatedFOGRA39.icc, although I must admit I am not that knowledgeable about color profiles in general.
So you're saying, if you're receiving web images and converting them for print purposes the USWebUncoated profile is generally the recommended one? If so I might try replacing the current one i'm using with that one in the future.