Export XMP sidecar files?

[GuidoGonzato]

Discussed in #323

^{Originally posted by GuidoGonzato October 19, 2023}
Dear all,
I've come to LightZone after using Ansel (the Darktable fork) for a while. I'm not a professional photograper / photo editor, and I find both programs brilliant - but LightZone is more intuitive and easier to use, IMHO.
One feature that I surely miss in LightZone is the creation of XMP sidecar files, which I find very convenient. I think it wouldn't be hard to implement it, and I hope to see this feature in LightZone soon.
My 2c.
Guido

[sfink16]

How do you use Ansel XMP sidecar? I just installed Ansel and I can see the "Create New Development" and Load Development from XMP". You can do a similar thing in Lightzone using the Lift tools (Found in the Browser window, just below the image), with the "Copy" tool on the left and the "Paste" tool on the right. You can also use the File/"Save as Style" to select tools in the toolstack in a new personal style. Is this what you are talking about, or is it something else?

[GuidoGonzato]

XMP files are very similar to toolstack files exported as Styles, but work on a per-image basis.
It works like this. In Ansel/Darkroom, whenever an image is edited a sidecar file is created/updated. It contains the full description of all operations performed on the file - just like a custom Style file in LightZone. In Ansel, when exporting the image to, say a jpg file, the sidecar XMP file will contain the change history and description, while the jpg file will not.
The advantage is clear: all changes reside in the XMP file, which is very small, and exporting to jpg is not necessary. Obviously, the contents of an XMP file can be applied to any other image.
It would be convenient if it were possibile to export the editing stack on a per-image basis instead of creating a new style. The sidecar files need not be proper XMP files, but follow the LightZone format.

[sfink16]

@GuidoGonzato Like I said, the (small) LZN file has the information an XMP would have, but it's just not easily readable as to what's in it. LZN files, like XMP files, are created after you edit an edit (raw or JPG). You can do a Lift (Copy)/Lift(Paste) without changing the LZN file you copied from. You can paste it to any and all image in your folder. My request of 313 is the same idea of using the copy/paste to view the changes from the Browser screens. Take a look at 313. At best, I see these two request as being combined together. Below is a partial example of the data (unformulated) what is in an LZN file: