GIMP: Re-uniting Save and Export (Shallow Thoughts)

Akkana's Musings on Open Source Computing, Science, and Nature.

Tue, 21 Aug 2012

GIMP: Re-uniting Save and Export

In GIMP 2.8, the developers changed the way you save files. "Save" is now used only for GIMP's native format, XCF (and compressed variants like .xcf.gz and .xcf.bz2). Other formats that may lose information on layers, fonts and other aspects of the edited image must be "Exported" rather than saved.

This has caused much consternation and flameage on the gimp-user mailing list, especially from people who use GIMP primarily for simple edits to JPEG or PNG files.

I don't particularly like the new model myself. Sometimes I use GIMP in the way the developers are encouraging, adding dozens of layers, fonts, layer masks and other effects. Much more often, I use GIMP to crop and rescale a handful of JPG photos I took with my camera on a hike. While I found it easy enough to adapt to using Ctrl-E (Export) instead of Ctrl-S (Save), it was annoying that when I exited the app, I'd always get am "Unsaved images" warning, and it was impossible to tell from the warning dialog which images were safely exported and which might not have been saved or exported at all.

But flaming on the mailing lists, much as some people seem to enjoy it (500 messages on the subject and still counting!) wasn't the answer. The developers have stated very clearly that they're not going to change the model back. So is there another solution?

Yes -- a very simple solution, in fact. Write a plug-in that saves or exports the current image back to its current file name, then marks it as clean so GIMP won't warn about it when you quit.

It turned out to be extremely easy to write, and you can get it here: GIMP: Save/export clean plug-in. If it suits your GIMP workflow, you can even bind it to Ctrl-S ... or any other key you like.

Warning: I deliberately did not add any "Are you sure you want to overwrite?" confirmation dialogs. This plug-in will overwrite your current file, without asking for permission. After all, that's its job. So be aware of that.

How it's written

Here are some details about how it works. Non software geeks can skip the rest of this article.

When I first looked into writing this, I was amazed at how simple it was: really just two lines of Python (plus the usual plug-in registration boilerplate).

    pdb.gimp_file_save(img, drawable, img.filename, img.filename)
    pdb.gimp_image_clean_all(img)

The first line saves the image back to its current filename. (The gimp-file-save PDB call still handles all types, not just XCF.) The second line marks the image as clean.

Both of those are PDB calls, which means that people who don't have GIMP Python could write script-fu to do this part.

So why didn't I use script-fu? Because I quickly found that if I bound the plug-in to Ctrl-S, I'd want to use it for new images -- images that don't have a filename yet. And for that, you need to pop up some sort of "Save as" dialog -- something Python can do easily, and Script-fu can't do at all.

A Save-as dialog with smart directory default

I couldn't use the standard GIMP save-as dialog: as far as I can tell, there's no way to call that dialog from a plug-in. But it turned out the GTK save-as dialog has no default directory to start in: you have to set the starting directory every time. So I needed a reasonable initial directory.

I didn't want to come up with some desktop twaddle like ~/My Pictures or whatever -- is there really anyone that model fits? Certainly not me. I debated maintaining a preference you could set, or saving the last used directory as a preference, but that complicates things and I wasn't sure it's really that helpful for most people anyway.

So I thought about where I usually want to save images in a GIMP session. Usually, I want to save them to the same directory where I've been saving other images in the same session, right?

I can figure that out by looping through all currently open images with for img in gimp.image_list() : and checking os.path.dirname(img.filename) for each one. Keep track of how many times each directory is being used; whichever is used the most times is probably where the user wants to store the next image.

Keeping count in Python

Looping through is easy, but what's the cleanest, most Pythonic way of maintaining the count for each directory and finding the most popular one? Naturally, Python has a class for that, collections.Counter.

Once I've counted everything, I can ask for the most common path. The code looks a bit complicated because most_common(1) returns a one-item list of a tuple of the single most common path and the number of times it's been used -- for instance, [ ('/home/akkana/public_html/images/birds', 5) ]. So the path is the first element of the first element, or most_common(1)[0][0]. Put it together:

    counts = collections.Counter()
    for img in gimp.image_list() :
        if img.filename :
            counts[os.path.dirname(img.filename)] += 1
    try :
        return counts.most_common(1)[0][0]
    except :
        return None

So that's the only tricky part of this plug-in. The rest is straightforward, and you can read the code on GitHub: save-export-clean.py.

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[ 11:26 Aug 21, 2012    More gimp | permalink to this entry | comments ]
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