Custom Exif Tags

Question

I am using exiv2 to manipulate metadata in a jpeg file. I need to write more information related to image processing into the metadata. Is is possible to create Custom Exif

Answer 1

From http://www.exif.org/Exif2-2.PDF:

D. Tags Relating to User Information

MakerNote
A tag for manufacturers of Exif writers to record any desired information. The contents are up to the manufacturer, but this tag should not be used for any other than its intended purpose.
Tag = 37500 (927C.H)
Type = UNDEFINED
Count = Any
Default = none

UserComment
A tag for Exif users to write keywords or comments on the image besides those in ImageDescription, and without the character code limitations of the ImageDescription tag.
Tag = 37510 (9286.H)
Type = UNDEFINED
Count = Any
Default = none

exiv2 supports MakerNote tags: http://dev.exiv2.org/projects/exiv2/wiki/How_to_add_support_for_a_new_makernote

If you don't want to do this, you can use UserComment: http://www.exiv2.org/doc/exifcomment_8cpp-example.html