improvable error message

[paolobenve]

exiv built without -DEXIV2_ENABLE_BMFF=1:

$ exiv2 -pp "/home/paolo/image.CR3"
Exiv2 exception in print action for file /home/paolo/image.CR3:
/home/paolo/image.CR3: The file contains data of an unknown image type

I think that the error message is correct, but could be better: actually exiv2 cannot find the preview because it hasn't the rights to process CR3 files. A check on CR3 type would permit to add a suggestion that maybe EXIV2_ENABLE_BMFF support isn't enabled.

[clanmills]

This was discussed and investigated a couple of weeks ago. The message results from the BMFF parser not being in the code base and therefore the file type is unknown. I looked at moving some of the BMFF code into every build so the image type would be recognised and a message such as you have suggested could be issued. I didn't want to restructure the code at v0.27.3 RC3.

The reason 0.27-maintenance uses a default of -DEXIV2_ENABLE_BMFF=0 is discussed here: https://github.com/Exiv2/exiv2/wiki/BMFF-Legals

The default for branch 'main' is -DEXIV2_ENABLE_BMFF=1 and therefore future exiv2 versions will support BMFF by default. So, this message will disappear.

[clanmills]

@paolobenve I'm going to close this. The changes required to fix this would require v0.27.5 RC4 and a three week delay. I'm sure you and the darktable folks prefer to have 0.27.5 now with the CR3/preview code.

As you know, Paolo we don't always get what we want. Team Exiv2 have worked well on your behalf and delivered CR3/preview for you.