Image compression DSP

Greetings,
  I am looking for a low power image compression for a mobile
application.  It is meant to compress image data from an image sensor
so it can be transmitted over GPRS.
  Does anyone have any recommendations?  Currently I am still looking
for a microcontroller, probably a PIC to do the control functions.  I
am not sure if any microcontroller will be fast enough to be able to
perform compression and control simultaneously.

  Any ideas will definitely be helpful.

The frame rate does not have to be high, perhaps one frame per sec for
a 640 by 480 monochrome image.