Imagick::setImageClipMask

<?php
function setImageClipMask($imagePath) {
    $imagick = new \Imagick();
    $imagick->readImage(realpath($imagePath));

    $width = $imagick->getImageWidth();
    $height = $imagick->getImageHeight();

    $clipMask = new \Imagick();
    $clipMask->newPseudoImage(
        $width,
        $height,
        "canvas:transparent"
    );

    $draw = new \ImagickDraw();
    $draw->setFillColor('white');
    $draw->circle(
        $width / 2,
        $height / 2,
        ($width / 2) + ($width / 4),
        $height / 2
    );
    $clipMask->drawImage($draw);
    $imagick->setImageClipMask($clipMask);

    $imagick->negateImage(false);
    $imagick->setFormat("png");

    header("Content-Type: image/png");
    echo $imagick->getImagesBlob();

}

?>