
$ ./pngexif -h

Usage: 
./pngexif                          - read PNG from stdin and write EXIF to stdout) 
./pngexif <png-infile> <exif-file> - read PNG from infile and write EXIF to outfile) 
./pngexif -e[xif] <exif-file>      - read PNG from stdin, add EXIF chunk and write PNG to stdout) 
./pngexif -e[xif] <exif-file> <png-infile> <png-outfile> 
                                   - read PNG from infile, add EXIF chunk and write to outfile)

