Transforms an image to a new colorspace, and then extracts a single channel so that the individual channel values can be viewed.
   
<?php
function transformImageColorspace($imagePath, $colorSpace, $channel) {
    $imagick = new \Imagick(realpath($imagePath));
    $imagick->transformimagecolorspace($colorSpace);
    //channel should be one of the channel constants e.g. \Imagick::CHANNEL_BLUE 
    $imagick->separateImageChannel($channel);
    header("Content-Type: image/jpg");
    echo $imagick->getImageBlob();
}
?>