convert-nonogramconvert-nonogram is a tool that converts images to nonograms. (Why don't we just use indexed PNGs as the standard interchange format for nonograms?) Currently, it only outputs the widely-used XML-based webpbn format and the olsak format.
I use convert-nonogram to evaluate the solvability of nonograms while editing them as an image. You can install it with cargo install convert-nonogram.
All images supported by the [image] crate are supported as input, but if you try to create JPEG nonograms, you're going to have a bad time.
pbnsolveThis is what I do, since [pbnsolve] provides useful information about difficulty. You'll have to download and install it [from a tarball].
Then, to evaluate an image, do:
convert-nonogram examples/tea.png | pbnsolve -tu
(-t requests detailed difficulty output, and -u requires checking for uniqueness. You can add -b to suppress output of the solved grid, but it's useful when debugging a non-unique nonogram)
Here's a somewhat tricky nonogram that's solveable with only single-line reasoning. The "Lines processed" (relative to "Lines in puzzle", which is the sum of the width and height) is the best indicator of difficulty, I think:
$ convert-nonogram examples/shirt_and_tie.png | pbnsolve -tu
UNIQUE LINE SOLUTION:
.........aaaa..
........a....aa
....aaaaaaa...a
...aa.....aa.ab
..aa.......aabb
..a...........b
..a...a.aaaaa.b
..a...a.a...a.b
.aa..aa.aaaaa.b
.a...aa.a...a.b
.a..aaa.a...a.b
aa..a.a..aaa..b
a...a.a......bb
a...a.a......bb
aaaaa.a......bb
ab.a..a......bb
a..a..a......bb
aaaa..a.......b
......aaaaa....
..........aaaaa
Cells Solved: 300 of 300
Lines in Puzzle: 35
Lines Processed: 149 (400%)
Exhaustive Search: 0 cells in 0 passes
Backtracking: 0 probes, 0 guesses, 0 backtracks
Probe Sequences: 0
Plod cycles: 1, Sprint cycles: 0
Cache Hits: 0/0 (0.0%) Adds: 0 Flushes: 0
Processing Time: 0.000205 sec
Here's the same nonogram with the button on the shirt sleeve removed. Now it requires backtracking to solve:
$ convert-nonogram examples/shirt_and_tie_no_button.png | pbnsolve -tu
UNIQUE SOLUTION:
.........aaaa..
........a....aa
....aaaaaaa...a
...aa.....aa.ab
..aa.......aabb
..a...........b
..a...a.aaaaa.b
..a...a.a...a.b
.aa..aa.aaaaa.b
.a...aa.a...a.b
.a..aaa.a...a.b
aa..a.a..aaa..b
a...a.a......bb
a...a.a......bb
aaaaa.a......bb
a..a..a......bb
a..a..a......bb
aaaa..a.......b
......aaaaa....
..........aaaaa
Cells Solved: 300 of 300
Lines in Puzzle: 35
Lines Processed: 1158 (3300%)
Exhaustive Search: 13 cells in 2 passes
Backtracking: 105 probes, 32 guesses, 32 backtracks
Probe Sequences: 32
Found Contradiction: 31 (0 adj, 31 2-neigh)
Found Solution: 1 (0 adj, 1 2-neigh)
Choose Optimum: 0 (0 adj, 0 2-neigh)
Total probes: 105 (0 adj, 105 2-neigh)
Plod cycles: 1, Sprint cycles: 0
Cache Hits: 576/1102 (52.0%) Adds: 494 Flushes: 0
Processing Time: 0.001668 sec
nonogridnonogrid can provide a better and more comprehensive visual representation of ambiguities in non-unique nonograms.
Make sure to install nonogrid with cargo install --features=xml,web nonogrid to allow parsing the XML format (and to enable directly downloading nonograms from the web, because why not). Then, to evaluate an image, do:
convert-nonogram examples/tea.png | nonogrid
The [Olsak solver] comes in a tarball and doesn't even have a makefile! (Just do gcc grid.c -o grid to build it.) It accepts a different input format.
convert-nonogram examples/tea.png --olsak | grid -