GSoC: explaining digiKam’s non-destructive editing concept

Hi digiKamers, hi KDErs, hi planet,

few days ago I blogged about the progress of non-destructive editing in digiKam. According to your comments, I take it that there is some misunderstaning in the whole concept. So let me explain it to you :)

The non-destructive editing will be done in such way, that if (and only if) you do some edit to some image, there is automatically created new file, which is a copy of the original with applied changes and with list of edits you've made saved in metadata. Next edit you do, is again applied to the same already-created version and the list of edits in metadata is updated. This is done for example for you to be able to edit the edited file with some external app, let's say GIMP. If there would be only the list of edits stored somewhere, you wouldn't be able to edit it with nothing else until you'd export it from digiKam.

However, when you do some non-reproducible changes, like using some effect, which uses random values for initialization, we need to preserve this exact output, because it can't be reproduced in the same way (thanks for the randomness), so this gets saved again to the same file, but next edit you'll do, will need to go to new file. This will still be presented as one version in digiKam. But there is some ideas about adjusting the nondeterministic filters in such way, that even those could be reproduced when the proper values are stored. This approach would be much better, but I'm not sure if that could be done. But we'll definitely look into it.

About the "Originals" folder. As I wrote, this is supposed to be fully customizable. Think about some photos you take, you pull out the card from your camera, stick it to your PC/notebook/netbook/whatever, do some changes in your digiKam and then you want to fly away with the card to give some presentation. But you want to show only the better versions (the edited ones) and not go through three almost-same pictures in presentation again and again. That's why there will be this option, to move the originals into some other folder, so you can still have them present, but they won't get in your way when not using digiKam. Also think about mobile phones. You connect your phone to your PC, do some changes and then you want to show your friends some photos you take, but again, you don't want to show the originals, you want to show only the better versions. Think about having 100 pictures and that you'll do some edits (autolevels for example) to 50 of them. Then you would have 150 images in your mobile gallery and you would show every second picture twice. Again, that's what the "Originals" folder is for. And again again, it will be customizable. Or optional if you want. So you can just turn it off completely and your images will stay all in the same place.

Then there is the version management. Every edit you do to the original file, will create another version. If you edit the already edited version, the it's simply saved to the already created version file. Only when editing the original you'll get a new version. Or you'll have a possibility to 'fork' it to manually to create a new version. So for example you do several crops to your images. You simply open the original, do one crop, new version is there, saved, ready for other operations. You switch back to the original, you do different crop and another version gets created, again, every other edit you'll do will be saved in this same file with updated metadata. No one-effect-one-file-thing. Then you should be able to display all your versions along. Something like virtual album. So you can see all your cropped images next to them. But not only cropped, imagine you do some color changes or some other effects. Then you can see all your versions next to each other and pick up the best.

Next thing is GUI. There will be some kind of indicator, that you have more than one version, or that you have done some edits and you're able to revert them. The looks of this is not clear yet. But we're open to any proposals or mockups you may have. Also, with every opened version, you'll see a list of changes you've made and you should be able to remove any edit in the list. It would be cool if you could simply change the edit's values and have it reapplied, but that will probably take some more time to accomplish. But I'd like to see that happened.

And if you're thinking about buttons in the editor GUI, Save As... definitely won't disappear. Probably Save button could go away as it will be automatically saved after each applied (meaning you click Ok) effect. Instead of Save button there could be a Fork button, which would create completely new version (copy of the current edited version). Other changes in the UI haven't been decided yet. I'm focusing on the foundation right now, GUI will come later (but soon;)

That's basically how the non-destructive editing will be done in digiKam. Hopefully it's much clearer now to all of you :)

Marty