I am still trying to understand how to open a JPEG file, extract the Exif header, add data to or change data in the Exif header, and then write the header back to the JPEG file so that it can be read by ExifPilot or some other PC application to confirm that the data was written as intended.
The documentation at http://libexif.sourceforge.net/api/ is good and I have studied some of the sample programs. I have not figured out how to structure data that I want to store in the Exif header into the correct format for one of the libexif functions to accept it.
Can anyone tell me where I can learn to do that?
I cannot find the equivalent API documentation for the libjpeg file jpeg-data.c and all of the functions therein. Can you tell me where to find it?