Hugin doesn't copy icc colour profiles to output

[Bruno Postle]

(reported by [e-mail])

Hugin copies lots of metadata from the first photo in the project to the final output, this is from src/hugin1/hugin/config_defaults:

#define HUGIN_EXIFTOOL_COPY_ARGS "-ImageDescription -Make -Model -Artist -WhitePoint -Copyright -GPS:all -DateTimeOriginal -CreateDate -UserComment -ColorSpace -OwnerName -SerialNumber"

It seems that it should also have these args:

  -icc_profile
  -xmp

In particular, if there is no icc profile then the enblend -c option has no effect.

[Yuv (yuv)]

adding a couple of arguments to src/hugin1/hugin/config_defaults.h is not difficult and the panoply of available tags (which I believe are CaSe SeNsItIve) are listed at http://search.cpan.org/~exiftool/Image-ExifTool-8.25/lib/Image/ExifTool/TagNames.pod

ICC_Profile seems to be a no brainer although somebody will have to test if it is enough to just specify ICC_Profile in the list or if the individual tags must be listed, and if so which ones do we need?

http://search.cpan.org/~exiftool/Image-ExifTool-8.25/lib/Image/ExifTool/TagNames.pod#ICC_Profile_Tags

There is however a problem. Highly unlikely, but what if the images to be merged have different color profiles? blindly copying the first image's profile is no good idea. I actually had a few such cases, where I mixed a traditional panorama with a superimposed historical photographic scan.

XMP I am not sure what would be the benefit.

http://search.cpan.org/~exiftool/Image-ExifTool-8.25/lib/Image/ExifTool/TagNames.pod#XMP_Tags

I don't see any point copying the XMP exif which is just a repeat of other exif data. Then much of the data is related to the conversion parameters of the individual photo in the RAW converter. This, again is not applicable to the whole panorama.

After spending a few minutes reading through the linked documentation my hypothesis is that:
- XMP has no useful information
- in terms of color correction it would make sense for Hugin to convert all input images to a single color space; and then write the information of that profile into the output.

[Bruno Postle (brunopostle)]

Photos taken at different time with different cameras are not going to align photometrically, so being able to convert everything to a single colourspace isn't going to be very useful to many people.

It isn't necessary for Hugin to understand profiles to create accurate output, since Hugin internally has a good response model, but we really do need to copy a profile if there is one.

At some point Hugin should read the icc profiles and use it to provide a colour corrected display in the preview etc... but this is a different issue.