JPEG encoder+decoder for J2ME with RGB565 byte stream

I need a JPEG encoder + decoder algorithms for J2ME running in a resource-constrained mobile phone device. Built-in Java algorithms cannot be used because they process data in ARGB8888 format which consumes too much memory. At no point shall data be stored in Image buffer. Instead, I want a decoder that outputs into RGB565 buffer (2 bytes per pixel). The decoder should also be able to downscale the input image during decoding to any output resolution smaller than the input JPEG size. The decoder must have very low RAM footprint and be able to decode e.g. a VGA size JPEG file into 640x480 RGB565 buffer without consuming more than 800kB of heap (output buffer included). In a similar fashion, the encoder needs to be able to encode RGB565 input buffer into JPEG file with minimal RAM footprint. JPEG compression settings must be configurable.