Composite two images with the 'mathematics' compose method
<?php
// Equivalent to running the command
// convert src1.png src2.png -compose mathematics -define compose:args="1,0,-0.5,0.5" -composite output.png
$src1 = new \Imagick("./src1.png");
$src2 = new \Imagick("./src2.png");
$src1->setImageVirtualPixelMethod(Imagick::VIRTUALPIXELMETHOD_TRANSPARENT);
$src1->setImageArtifact('compose:args', "1,0,-0.5,0.5");
$src1->compositeImage($src2, Imagick::COMPOSITE_MATHEMATICS, 0, 0);
$src1->writeImage("./output.png");
?>