2 Color Image "Fast" saving from flash to php?

Hello all. I’m working on a program in AS2 that involves saving large images (up to 600x600 pixels) and am looking for a solution to save on server processing. The image will only be saved as 2 color .png and I’m thinking that should speed things up, however I haven’t found any examples of saving something other than full color images.
The full color image saving code I have found really takes time to process on the server. Anyone know of an example of saving a limited color image using as2/php that can be done fairly quickly?

P.S. It’s too late in the project to switch to AS3 so that will have to wait.