Batch edit of IPTC tags

[Bezierr]

Hi there,

another proposal. As always, feel free to reject if you don't like it, or don't think it's suitable for general RawTherapee.

This adds the functionality to batch edit IPTC tags -- something that I was used to in Lightroom but missing from RawTherapee.

The fact that IPTC tags are, unlike other parameters, not individual values but contained in a single map, gave me some headache. For everything I have tested, my solution works, but it may well be that, for a more experienced RawTherapee developer, there would have been a better way to do this.

Logic is as follows:

• For everything except keywords and supplemental categories: A tag value entered for the first selected picture will replace existing values in all other selected pictures. If the new tag value is empty, tag values will be replaced by the empty string, i.e. deleted.
• For keywords and supplemental categories: An entry added to the first selected picture will be added to all other selected pictures unless it already exists. An entry deleted from the first selected picture will be deleted from all other selected pictures provided it was there. Empty strings will be treated just like any other entries.

This logic is, I believe, in line with the behavior one would expect, and with the way how batch editing works for other parameters. Since values are not numeric, the distinction between "add" and "replace" does not make sense; therefore, no changes to Preferences/Batch Processing.

Tested quite extensively for Linux, not for the other OS.

Side note: When working on this, I found that I needed some automatism for initializing all pictures before batch editing them (setting IPTC tags is usually the very first thing I do), since I kept forgetting to do it manually. Which was the reason for my "initialization" proposal some time ago. Thanks for your comments there; I'll look into that one again as soon as I find the time.

[Lawrence37]

Nice work!

Since values are not numeric, the distinction between "add" and "replace" does not make sense; therefore, no changes to Preferences/Batch Processing.

For keywords and supplemental categories, a set mode could do a replacement, though I'm not sure how useful that would be.

[Bezierr]

I had thought about this replacement functionality myself, but given that (a) I personally have never missed it, and (b) all the programs I know don't provide it, I thought it would be better to not unnecessarily complicate things. So I'd propose to leave it as it is (provided nobody finds any bugs, of course) for the time being.