Canon/Nikon/other cameras save raw output of their sensor in some of their proprietary formats (.CR2, whatever). Is there any Java library designed to read them and convert
Unless you want to write you own file parser/loader (sounds fun imho ;) ), perhaps JMagick will help you. I haven't tried it and it might not work given your target platform since JMagick uses JNI.
UPDATE: dcraw looks like a good resource/reference