converting a web project from using PHP:GD to using GraphicsMagick, how do I call convert -colorize?

[xekon]

I am coverting a web project from using PHP-GD to using GraphicsMagick. One part of the project involves base PNG picture and for that picture that are 15 or so possible PNG pictures with transparency that can be overlayed on the base picture, and then color applied to them. It is basically a manikin, and the all of the overlay PNG pictures are items, coat, glasses, hat, shirt, shoes, etc. and I would overlay them. (I am not sure if this is even the best way to solve this problem, but it does work, if there's a better solution you can think of please let me know)

and I see that GraphicsMagick also has a way to colorize using gm convert -colorize: http://www.graphicsmagick.org/convert.html
With the GraphicsMagick PHP wrapper gmagick, I do not see way to call this function. I am hoping I am just overlooking it.

I am running
Ubuntu 14.04 x64
PHP_VERSION 5.5.9-1ubuntu4.5
gmagick version 1.1.7RC2
GraphicsMagick version GraphicsMagick 1.3.18 2013-03-10 Q8

Thanks for any help, I do appreciate it.

EDIT: I have looked high and low and it appears this function of GraphicsMagick is not available with php using gmagick, I am going to attempt to add this functionality to gmagick.