libjpeg API and Reference

This question is 7 years old now, and the libjpeg project has become stagnant. However, the libjpeg-turbo project appears to be its successor, and it is backwards-compatible with the old libjpeg API.

There is some documentation in libjpeg.txt. libjpeg is a very low-level, steep-learning-curve, old school c library. To use it effectively you need to be familiar with setjmp and longjmp, c structure layouts, function pointers, and lots of other low-level C stuff. It's a bear to work with but possible to do a great deal with minimal resource usage.

The documentation is not that great. I think the authors intended that anybody using this library would be able to read through the source and figure out how the stuff works.

The main API files would be jpeglib.h and jerror.h. You can find these files as part of standard Android distribution also.jpeglib.h contains all the data structures, whereas jerror.h contains all error codes with corresponding messages.