(Modified 2013 Jun 03)
Re-saving as JPG
With GIMP version 2.8, the developers decided that users needed to be protected from themselves, and started to require exporting a copy of the working file to JPG format, with the intention of saving the altered file to XCF format. (If the file was merely exported, upon closing, GIMP would pop up a reminder that there were unsaved changes.) The main benefit is that attributes such as layers would otherwise get lost if the file was accidentally saved as a JPG. Casual users such as myself use a layered image less than 2% of the time. Apparently, the technology to check whether an image has layers is not yet available.
Akkana Peck wrote a workaround plugin to restore the pre-2.8 behavior (or close to it, as far as I can tell). It is described at her blog. The script is GitHub. I don't know how to download the Python script other than copying & pasting it; I saved a copy here. To enable it (in Linux), save it to your .gimp-2.8/plug-ins/ directory, and change it to an executable. The next time you start GIMP, there will be an option Save/Export clean under File. I bound CTRL-s to it under Edit > Keyboard Shortcuts .
It's been a while since I saw such a willful example of utter contempt for one's user base, complicating something as simple as saving a file. For comparison, LibreOffice asked once, if I recall, whether I wanted to save a file in its native format, but I was allowed to silence that reminder.
I was tempted to downgrade to version 2.6, but I was intrigued to try the new single-window mode in version 2.8. I also will be experimenting with other image editors. fotoxx seems promising, and I'll keep an eye on pinta. GIMP is for the moment still the best game in town, but the arrows are pointed downward.
And I'll probably want to stop using GIMP's mascot Wilber in Tux Racer.
Using guides freezes pointer
In XFCE (version 4.4 was okay, 4.8 is not), dragging a ruler freezes the pointer in some weird state, where I can't click on menus or activate a terminal window. (I found that switching from and back to that desktop restores my ability to use that terminal.)
This bug was reported in GNOME's Bugzilla. Bizarrely, the fix is to kill xscreensaver, i.e.:
Hopefully, this bug gets fixed soon. (Maybe it has already.) By the way, to reactivate xscreensaver, what worked for me was:
GIMP can stitch panoramas together using pandora. Its package will need to be installed independently of GIMP. To stitch photos, the command is under Filters near the bottom. I haven't figured out what the Pandora menu is for yet. Lately, I've been using hugin for panoramas, which is more automatic.
Also, when selecting images to stitch, the window may be taller than the screen on smaller displays, such as netbooks. In order to click OK, you will need to Alt-drag the window upward.
Wavelet denoising was a recommended way to smooth images suffering from high-ISO noise. On Ubuntu, it is installed with the package gimp-plugin-registry. A moderate filtration level is to select Channel Y, and use a Threshold of 0.75. A more conservative filtration level is 0.33. The filtration can be repeated with CTRL-F.
Batch-processing -- Auto white-balance
I don't 100% understand the syntax, but I imagine I'll learn as I use batch-processing more. The need that motivated me to learn was the discovery of the usefulness of auto white-balance. For dark photos, even slightly dark, it's probably worth running routinely.
The batch script, I copied from the blog of Emery Clark. The script is here. Save it to /home/YOUR_USERNAME/.gimp-2.6/scripts, substituting the appropriate username and version of GIMP. The command-line usage is:
gimp -i -b '(batch-levels-stretch "*.JPG")' -b '(gimp-quit 0)'
Change the file pattern (e.g., "*.JPG") as needed.
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