At the back of my mind I sort of have to agree with you, but practically speaking I don’t see any one having the time and expertise to add something like it to Gramps.
Sure, the convenience of doing it all in one app looks attractive, but one of the biggest problems, aside from making Gramps even bigger, is that there is, to my knowledge, no standard setting out which tag should hold which data.
It seems there have been some starts at some sort of standard, but nothing has matured, AFAIK
There is: https://www.facebook.com/groups/www.fhmwg.org but it has been so quiet, too quiet, for my liking.
One of my favorite libraries at this stage is Exiftool. My Windows app interfaces to it, simply because, currently it is the most up-to-date and actively developed library in the metadata domain.
But, on last count, that library list some 27 000+ tags
This means that if one would want to have Gramps edit any metadata, most folks would expect that their favorite field/tag is supported.
Hence Gramps would need a way to make these choices user selectable. Granted many tags are most unlikely to be of interest, but even so, that leaves a big pile.
Add to that, that none of the currently defined tags were designed with genealogy needs in mind and most of the ones which might seem useful, such as the ones meant for time, dates, location, generally have several variations on the exact meaning.
There is another issue at the bottom of all of this and I have not seen it discussed anywhere, though I have not really looked very hard.
It is this:
Each image file is composed of several sections. Some of these contain the actual image data - which is encoded in different ways, depending on both the file type/extension and other specific options, such as compression type and ratio, specially for jpg images.
The metadata typically resides in one or more separate chunks. When apps edit the metadata, they are free to move these chunks about in the final image file written to disk. What is worse, not all available utilities offered for editing the metadata follow all of the rules set out by the standards.
Based on my current understanding of the media verify tool, it computes some sort of checksum over the whole file. This means that every time you modify even one byte in the metadata, that checksum will change.
How Gramps and each user will handle this aspect, we’ll have to see.Should Gramps compute several checksums? one for the actual image data and a separate one for metadata?
My current preference would be to make Gramps display all metadata in an image and allow the user to inspect it, copy it to another app via the clipboard for updating and ensure Gramps reloads the image quickly so that the user can verify the result.
That is what I am aiming for, but of course, those are simply intentions right now, though I am hoping that I will be able to progress along the way well enough to make it useful with time.
Partly because I do not want to be bound by choices made already in the currently available plugins, I intend to start from scratch and, FWIW, hope to be able to use Exiftool as the backend
That is where I am at today