Adjust Wordpress Plugin (Fancy product designer) - add PNG masking ability

We need to make an adjustment to the wp plugin: Fancy Product Designer [login to view URL] This plugin is based on fabric JS ([login to view URL]) this is the core HTML 5 canvace. The plugin have the ability to create a bounding box limitation for the images uploaded, and use a layer's bounding box as limitation and mask for other layers. This bounding box masking feature only takes the rectangular boundary of the image as the mask. We need this feature to be changed to make it take the exact shape of the PNG image as the mask. The [login to view URL] has the ability to use PNG images as masks for other images using (Mask Class) Below you can find Mask class examples: [login to view URL] [login to view URL] So we need the mask class applied instead of the bounding box feature in the plugin. We will provide you with the plugin files in order to work on.