number-loom

number-loom is a powerful tool for constructing puzzles variously known as "Nonograms", "Paint By Numbers", "Griddlers" (and many other names).

Spot a change that makes the puzzle totally solveable and still look good!

It's still pretty janky, but it's also the most powerful such tool I know of. In particular, it can offer suggestions for how to make an unsolveable puzzle more solveable! You can use it in your browser, or install it on your own machine (see below).

Features

• Supports the following file formats:
  • webpbn's XML-based format (extension: .xml or .pbn)
  • The format used by the Olšák solver (extension: .g)
  • Images (typical extension: .png)
  • char-grid, a plaintext grid of characters, which it attempts to infer a reasonable character-to-color mapping (extension: .txt)
  • .woven, a format designed for Number Loom, mostly to facilitate transmitting puzzles as short(ish) text strings.
  • HTML, for export only, as a printable puzzle (extension .html)
• Has support for "Trianograms", a rare variation with triangular cells that may appear as caps to clues.
• An exhaustive line-logic solver that provides some difficulty information.
• "Disambiguator": a tool that searches for one-cell edits that make puzzles closer to solveable.
• A mode for test-solving, with a variety of toggleable assistance features:
  • Immediate error reporting
  • Limited background square inference
  • Indicators on lines for whether clues can make progress

Installation and usage

number-loom can run in your browser! I've published it at https://paul-stansifer.itch.io/number-loom.

You can also install it to your machine if you're comfortable with the command line. The first step is to install cargo through rustup if you haven't already.

Then run cargo install number-loom.

To open the gui: number-loom or number-loom examples/png/keys.png --gui.

To solve a puzzle from the command line, do number-loom examples/png/hair_dryer.png. Adding --disambiguate will attempt to find disambiguations if it can't solve it.

To convert a puzzle from the command line, do number-loom examples/png/hair_dryer.png /tmp/hair_dryer.xml. Use --input-format or --output-format if you want to explicitly select a format: webpbn, olsak, image, char-grid, or html. (The image format is still inferred from the filename.)

Solver

The number-loom solver is a line-logic solver only.

Internally, it has two modes:

• "skim", which shoves all clues in a line as far as possible to one side and then the other, and checks to see if any of the clues (or gaps) overlap themselves between the two positions.
• "scrub", which determines all possible locations of each clue, and then observes what cells are fixed. This gets all information it is possible to get from a particular line.

It stores progress by noting each possibly-remaining color in each cell. Even though a human solver typically only notes down known cells, in my experience this corresponds pretty well to the sort of ad-hoc logic that solvers perform on color nonograms when they glance at the both lines that contain a cell.

Looking at the number of scrubs and skims can tell you something about the difficulty of a puzzle. Unless you're aiming for an easy puzzle, the solver should have to do some scrubs. If the number of scrubs is higher than the width plus the length, or the number of skims is more than five times that, it's probably tedious relative to the size of the puzzle. This is a very rough guide: you should test-solve your puzzle to get an accurate view of the experience (click the "Puzzle" button!).

GUI

Edit mode

When editing a nonogram, you can:

• Paint by dragging / draw orthographic lines / flood fill
• Adjust the size of the canvas from any side
• Undo or redo with buttons or the "Z" and "Y" keys
• Add, remove, or recolor palette entries
• Solve the puzzle (it paints gray dots over unsolved cells), optionally automatically after each edit
• Disambiguate
• Switch to "Puzzle" mode to test-solve
• Edit metadata: title, description, author and license. The title is intended to be displayed before the puzzle is solved, and the description is intended for display afterward.

Disambiguation

This may take a little bit of time, but it's typically reasonably fast for puzzles under 40x40. Cells will get a small square with an alternate color, with an opacity proportional to the number of unsolved cells that are resolved if that single cell is changed to that color. (It only ever displays one color, but there might be others that work just as well!)

It works by simply re-solving the puzzle with every possible one-square change. But it caches intermediate deductions to speed the process up. Typically, the more ambiguous the puzzle, the faster it is, so doing a guess-and-check with "auto-solve" turned on is sometimes a better way to hammer out small remaining ambiguities.

Puzzle mode

In puzzle mode, primary click paints the currently-selected color, right-click paints blank squares, and middle-click paints "unsolved" (undo/redo also work). There's also a counter widget that helps you measure the contiguous region that you're in. There are also some toggleable assistance features (which can either be invoked immediately or automatically after each change):

• Detection of errors
• Inference of "obvious" background squares
• Indicators on lines that can be progressed

Note: indicators only appear if some cell on a line can be fully solved. However, the automatic solver can "partially solve" cells by ruling out some colors, and that partial information can be used by other lines. Therefore, on multicolor puzzles, it's possible for a solveable puzzle to at some point have no line-progress indicators!

Trianograms

Trianograms are a rare variant. "Mindful Puzzle Books" publishes a book by that name. The Olšák solver also supports this variant, crediting the concept to "the journal Maľované krížovky, Silentium s.r.o, Bratislava", but I haven't been able to find out more. There are puzzles with triangles at griddlers.net, but I think they are merely traditional nonograms with triangular colors.

A Trianogram has black, white, and four additional "colors": triangles that divide the cell into half-black and half-white. The triangles always serve as "caps" to a clue; for example "◢2◤" denotes that the four cells "◢■■◤" will appear. They will be consecutive, despite the fact that the caps are different "colors". Two consecutive clues will only be guaranteed to be separated by a space if neither of them is capped on the facing sides (if there are multiple identical consecutive triangles, they will each get their own clue).

The Olšák solver, I believe, supports multi-color trianograms, but number-loom does not yet.

Only the olsak and char-grid formats can store trianograms.

The "webpbn" format supports "triangular colors", but it does not support "clue cap" notion from trianograms; it's a purely cosmetic variation.

Usage with other solvers

pbnsolve

You'll have to download and install pbnsolve from a tarball (and probably edit the Makefile to help it find libxml2 -- under Ubuntu, you'll need to do sudo apt install libxml2-dev). Then (assuming it's on your $PATH):

number-loom examples/png/stroller.png - --output-format webpbn | pbnsolve -tu

It gives some difficulty information. I believe that "Lines Processed" very roughly corresponds to number-loom's measurement of skims and scrubs (summed together). number-loom should be equivalent to pbnsolve's -aE mode, though pbnsolve can handle any solveable nonogram by doing a counterfactual tree search.

The Olšák solver

The Olšák 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. It does provide some difficulty information, but I haven't yet learned to understand it.

number-loom examples/png/stroller.png - --output-format olsak | grid -