Converting .gif to .png format in Cocoa (OSX) without using representationUsingType:properties:

Question

I need to write a method that takes a .gif image file as input and converts it to a 32x32 .png file. The only way I found to do this in Cocoa would be using the representationUsingType:properties: method of NsBitmapImageRep but unfortunatley I cannot use this method because it is not supported by cocotron (an open source API that implements the Cocoa API for Windows) and I need to use this method in a cross platform app. Can anyone suggest another way to do this conversion with Cocotron.