Tear-off

As a technical editor/writer, I found the need for a plugin to easily crop application screenshots with that somewhat jagged "torn-off" appearance. I found a way to manually obtain the effect I needed, and simply replicated the steps in a Python script, using the gimpfu module.

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07 Jul 2010: UPDATED to v 0.2 by Tracy S. Fitch -- now Windows 7-compatible, plus several other changes (changelog is below). A huge thank-you to Tracy for the major work, and for the major courtesy of sending the updated script to me to update this post!
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To install the plugin:
1. Put the Python file (rename the v0.2 file to remove the annoying .txt extension that this site adds automatically) in the plug-ins folder in the GIMP settings folder in your home folder (or your user settings folder on Windows). That is, if you're using GIMP 2.6 under Linux, the folder would be ~/.gimp-2.6/plug-ins/. Under Windows, you could go to C:\Documents and Settings\\ and search for folders whose names contain "gimp", then go to the plug-ins folder under that.
2. Under Linux, make the file executable (chmod u+x scrnshot_tearoff.py). This is not required for Windows.
3. (Added thanks to comments) If you don't have Python and PyGTK installed, you'll need to install them. This is most likely to happen for Windows computers; many Linux distributions install Python by default. Head to http://www.python.org/download/ and http://www.pygtk.org/downloads.html for Windows installables; for Linux, use your distribution's package management tool to look for and install Python and PyGTK.
4. (Re)start GIMP.

The original plugin script puts a "Tear-off" menu item on the Image menu for all image windows only (that is, no menu option is available in the main GIMP Toolbox window's menus). Tracy's v0.2 has the menu option at Filters > Distort > Tear-off. Capture your screenshot, or open a saved image; select the area of the image that you want to keep; click the plugin's menu to get a dialog where you can modify the plug-in parameters.

This script should run in the following environments:
- Ubuntu Linux 7.10, 8.10, 9.04, 10.04 // Python 2.5.1 to 2.6.x// GIMP 2.4.2 to 2.6.8
- (from the comments) Mac OS X (10.5.7)
- (thanks to Tracy!) Windows 7, GIMP 2.6.9, Python 2.6.4, pygtk-2.16, pycairo-1.8.6, pygobject-2.20
- as per zemalf's comment, "Gimp 2.6.8 (with Windows XP & latest stuff, like GTK+bundle 2.18.7, pygtk 2.16, pyobject 2.20, pycairo 1.8.6)" with the changes listed in the comment.

Changelog for v0.2 (attachment filename scrnshot_tearoff_v0.2_TSF.py.txt :-/ ):
#Version: 0.2 2010-07-05 -- Tracy S. Fitch (thespian at bigfoot.com) -- Windows Compatible
# Known Issues:
# - still no real testing -- just one more platform:
# - Windows 7 (Version 6.1.7600)
# - GIMP 2.6.9
# - Python 2.6.4
# - pygtk-2.16
# - pycairo-1.8.6
# - pygobject-2.20
#
# Changes:
# - switched to current directory log file (should be Linux/Win safe)
# - divided logging into progress, debug, error, & none
# - added progress bar updates & pulses
# - moved menu path to a separate value in register statement
# - moved to filters->distorts since it seems similar to page curl
# - added optional border function (default on)
# - modified resizing after drop shadow to only add in the shadow direction
# - rearranged layers to put shadow on the bottom
# - linked shadow and border layers to the original image
# - optional merging of border and shadow layers (default on)
# - formatted dialog (to the extent I can figure out how to format gimpfu's dialog)

Footnote: if, like me, you have a vertically-challenged display (my laptop runs 1366x768 pixels) then the lower portion of the parameters dialog may "fall off" the screen. Under Linux, you can hold down Alt, click on any blank area of the dialog, and drag it up to view the rest of the dialog. Under Windows, Alt+Spacebar > Move, and hitting the Up arrow key several times, should do the trick. Unfortunately, the gimpfu method of creating plugins leaves little scope for making the dialog broader, not taller :-( Sorry.