If you have a monochrome image that you want to make a puzzle from, you can use the nonogram command in the package nonogram to generate and test the puzzle. For example, on a UNIX system, suppose that your puzzle image is an X bitmap called wibble.xbm. To convert it to the puzzle format used by nonogram, use:

bmtoa wibble.xbm | nonogram -is -o wibble.non -g

The puzzle is placed in the file wibble.non.

For other formats, pipe the image through convert first:

convert wibble.png xbm:- | bmtoa | nonogram -is -o wibble.non -g

One can't just use any old pattern to build a Nonogram. Many different images may generate the same puzzle, so the solver has no logical way to tell which is the intended.

Also, some puzzles, though having only one solution, require so much trial-and-error guessing that it becomes awkward to manually keep track of what has been guessed.

To test that the puzzle has only a single solution, use:

nonogram -i wibble.non -s 2 -CO +o

This will count the number of solutions, without displaying them, stopping after the first two. It prints ‘1’, therefore, only if the puzzle has a single solution.

On other sites, and maybe in puzzle books too, you might encounter colour Nonograms. These will usually have one or two extra colours as well as solids and dots (often black and white, respectively).

To make such a puzzle, you must specify each block's colour, if it isn't black, either by writing the block's length in that colour, or by using a code (such as ‘R’ for ‘red’). Remember not to give the lengths of white (dot) ‘blocks’, or you'll give the game away.

Unfortunately, my own site does not support colours (yet).