Turn your picture into a puzzle

Give a jpg- file. (Other file-formats are also allowed — usually.)
This image is used to build a nonogram [Wikipedia; explanation; example puzzle with Alan Turing].
It takes some time ... in particular if the file is large (so please do not use images larger than 100 kB;
larger than 500 kB is even forbidden),
or if threshold value and stepsize happen to be "wrong".

The `jpg`-file:
Height:
Width:
Edge:
Threshold:
Stepsize:
Difficulty:	normal hard very hard

The higher the "threshold" value, the darker the final picture. At this threshold value the search for a uniquely solvable puzzle begins, and the "stepsize" determines how the possible values are tried.
"Height" and "width" determine maximal values; the original image ratio is maintained — more or less.
The "edge" parameter allows for some contour manipulation within the image.
The "difficulty" parameter speaks for itself ... but is experimental, takes more time for hard puzzles, and then sometimes still gives an easy puzzle.

Questions/remarks: kosters@liacs.nl

Walter Kosters, October 20, 2008 — http://www.liacs.nl/home/kosters/nono/indexeng.html