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Copyright (C) 2013 Aaron Miller. All rights reversed. Share and Enjoy!
Last revision: Thursday, December 26, 2013, ca. 06:30.
Author: Aaron Miller [email protected]
Websites such as FileFormat.info's Unicode Upside-Down Converter establish a mapping between a range of Unicode characters (usually alphanumerics and a selected set of punctuation) and characters which resemble their upside-down versions, and use it to transform a given string of text into its visually inverted version. I saw no reason not to do something similar in Emacs. This is that thing.
To use this code, drop this file into your Emacs load path, then (require 'upside-down). The library defines two functions: 'upside-down-invert-string', which takes a string argument and returns the upside-down version, and 'upside-down-replace-region', which applies that transformation to the active region, and which can be called interactively. Also defined is the variable `upside-down-mapping', which contains an alist mapping characters with their upside-down versions, in case you have some other use for that.
Possibly of interest is that the transform implemented by
'upside-down-invert-string' is its own inverse, such that
(string= "string" (upside-down-invert-string (upside-down-invert-string "string")))
evaluates to T.
Some of the digits are mapped poorly, 5 in particular.
Much of the mapping defined in this library comes from FileFormat.info's converter, with significant improvements made possible by Shapecatcher.com's Unicode character recognition service, which takes a hand-drawn representation of the character you want and finds the most visually similar among its database of ca. 12000 characters.
The canonical version of this file is hosted in my Github repository. If you didn't get it from there, great! I'm happy to hear my humble efforts have achieved wide enough interest to result in a fork hosted somewhere else. I'd be obliged if you'd drop me a line to let me know about it.