[Libjpeg-devel-6x] Can we rewrite tags after compress is finished?

[Drip S. <dri...@gm...>]

Hello,

I am working on a small project which needs to rewrite a tag after
jpeg_finish_compress( &cinfo ); is called.

The procedure is:

1. jpeg_write_marker
...
2. while(...)
    jpeg_write_scanlines
...
3. jpeg_finish_compress
4. update the marker we have written

The tag I have written first is not correct because it needs the size
of jpeg file. I plan to update the tag after jpeg_finish_compress. Is
it possible to tell the position of each tag before writing it to the file
so that I can rewrite it without parsing jpeg file again. I tried ftell(),
and it doesn't work well.


Thanks a lot!
Dripstone