Well i figured out how to extract the alpha from transparency in photoshop by creating a “Layer Mask > From Transparency” and then create the alpha channel from that. But Photoshop wont save the channel when saving the file as a PNG.
Here’s the link I found that give a bit of info on doing this.
http://helpx.adobe.com/experience-manager/scene7/kb/base/transparency-alpha-channel/layer-transparency-masks-alpha-channels.html