The attached zip file now includes a Python version of the Post Rotate Crop script. This runs very much faster than the Script-Fu version (which is also included in the zip file for those who don't have Python installed).
Whilst originally intended to be used following a rotation the script can also be used following
other transformations, such as perspective, scale and shear. The transparent areas added to the
image by the transformation are removed to leave an opaque rectangle.
The script provides options that determine how the resulting rectangle should be maximized.