AppMsgBridge allows native Android companion development of Pebble apps from the Pebble emulator. It is a simple python implementation of a bridge (adapted from the phone simulator code) and an Android app that sniffs the AppMessage intents and forwards them to the python bridge.
While trying to get png images working for Pebble Time, there was quite a lot of discussion in the community about some of the shortcomings of various libraries and incompatibilities.
On Android the lack of the Java imaging libs and AWT stops you from using a lot of the mainstream imaging tools. I use a combination of a hacked PngEncoder (originally by J. David Eisenberg in 2003!) and android-jhlabs
My PngEncoder is here along with an example where I use jhlabs to resize and dither then create a png8.
Feel free to suggest improvements it is still work in progress and the gist is hard coded to png8 right now.
Android jhlabs is here: