Can you define what makes a proper RAW &quot;decoder&quot;? We actually discuss about RAW decoding here. Adobe offers the DNG SDK as open source, it gives quite good clue on how to process RAW images, alternatively dcraw from Dave Coffin has been online for ages and is the basis (in a way or another) of most of open source RAW processing software. Once the CFA bayer (or other mosaicing type) data is available (decrypted as it is crypted for quite a few camera makers), the demosaicing performed and the photo white-balanced and exported with its full dynamic range in a RGB colourspace, you have done most of the technical steps to start working creatively with it.