Picross Solver Library

Picross is a puzzle game, also called nonogram or paint-by-number. The goal is to find a hidden picture in a rectangular grid, by painting some of the cells with one color, or leaving them blank. The information given is, for each row and each column, the number and size of the segments of continuous filled cells on that line.

This is a solver library for picross puzzles. The solver will find the solutions of a grid based on the row and column constraints given as input. The solver handles grids with multiple solutions and can be used as a validator to check the uniqueness of the solution.

Features

• The solver library has no dependencies other than C++17
• Compilation of the library is checked against: MSVC, gcc, clang.
• Black and white puzzles only
• Handle puzzles with multiple solutons and check for uniqueness
• Three puzzle file formats are supported:
  • Steve Simpson's NON format
  • Jakub Wilk's NIN format
  • A native format created for this library
• Fast, and battle-tested on a wide range of puzzles: Performance
• Two applications on top of the library: CLI and GUI.
• Use the GUI to make your own picross puzzles!

There's a demo video: Here!

Library

The Picross solver provided as a library

Build

With CMake. For example on Windows:

mkdir ./build
cd build
cmake -G "Visual Studio 17 2022" ..
cmake --build . --config Release

Unit Tests

Dependencies:

• Catch2
• PNM++

Build and run unit tests:

cmake -G "Visual Studio 17 2022" -DPICROSS_BUILD_TESTS=ON ..
cmake --build . --target run_utests_picross --config Debug

Install

Install in some dir:

cmake --install . --config Release --prefix <some_dir>

Or, package the library:

cpack -G ZIP -C Release

CMake Integration

The library CMake's build exports the following target: picross::picross

Example

Below is an example of how to use the library. The API is accessible via a unique header file <picross/picross.h>

Source: example_1.cpp

#include <picross/picross.h>

#include <cassert>
#include <cstdlib>
#include <iostream>

int main()
{
    // Puzzle definition
    const picross::InputGrid::Constraints rows {
        { 3 },
        { 1, 1 },
        { 1, 1 },
        { 3 },
        { 3 },
        { }
    };
    const picross::InputGrid::Constraints cols {
        { },
        { 2 },
        { 2 },
        { 5 },
        { 1 },
        { 3 }
    };
    picross::InputGrid puzzle(rows, cols, "Note");

    // [Optional] Check the puzzle validity
    const auto [check_is_ok, check_msg] = picross::check_input_grid(puzzle);
    if (!check_is_ok)
        return EXIT_FAILURE;

    // Solve the puzzle
    const auto solver = picross::get_ref_solver();
    assert(solver);
    constexpr unsigned int max_nb_solutions = 2;
    const auto result = solver->solve(puzzle, max_nb_solutions);
    if (result.status != picross::Solver::Status::OK)
        return EXIT_FAILURE;

    // Print out the solutions
    assert(!result.solutions.empty());
    for (const auto& solution : result.solutions)
        std::cout << solution.grid << std::endl;

    return EXIT_SUCCESS;
}

Output:

...###
...#.#
...#.#
.###..
.###..
......

Applications

A CLI and a GUI applications built on top of the solver library.

The applications are able to read puzzle files in the formats listed above for the library, and also raw images in the following formats:

• Bitmap: PBM files
• Raw text with the '.' and '#' characters: Example
• Raw text with the '0' and '1' characters: Example

Dependencies

Common to all:

• PNM++

Command line interface:

• Argagg

Graphical UI:

• OpenGL
• GLFW3
• Dear ImGui
• Portable File Dialogs

Build

On Windows:

mkdir ./build
cd build
cmake -G "Visual Studio 17 2022" -DPICROSS_BUILD_APP=ON -DPICROSS_BUILD_CLI=ON ..
cmake --build . --config Release

Command Line Tool Usage

Basic Usage

Run the CLI on the example file:

./build/bin/Release/picross_solver_cli.exe inputs/example_input.txt

Validation Mode

Use the validation mode to test multiple files at once and check the uniqueness of the solution.

• Output one line per puzzle, in a comma-separated format.
• Validation is OK if the puzzle is valid and has a unique solution
• Difficulty hint: LINE for puzzles that are line solvable, BRANCH for puzzles that have a unique solution but are not line solvable, and MULT for grids with multiple solutions.
• Performance timing

For example:

./build/bin/Release/picross_solver_cli.exe --validation ./inputs/example_input.txt ./inputs/domino_logic.txt

The output, in CSV format, will contain the following information:

File	Grid	Size	Valid	Difficulty	Solutions	Timing (ms)
example_input.txt	Fish	22x20	OK	LINE	1	0.4495
example_input.txt	Two Notes	10x10	MULT	MULT	2	0.668
domino_logic.txt	3-Dom	7x7	OK	BRANCH	1	0.0981
domino_logic.txt	4-Dom	9x9	OK	BRANCH	1	0.855
domino_logic.txt	5-Dom	11x11	OK	BRANCH	1	4.0144
domino_logic.txt	6-Dom	13x13	OK	BRANCH	1	15.402
domino_logic.txt	7-Dom	15x15	OK	BRANCH	1	159.027
domino_logic.txt	8-Dom	17x17	OK	BRANCH	1	1628
domino_logic.txt	9-Dom	19x19	OK	BRANCH	1	21867.5

Make your own Puzzles with the GUI

See tutorial here.

Screenshots of the GUI

The GUI shows an animation of the solving process, and finally the solution(s). Here are two examples from the game Picross DS:

The hardest puzzles are not line solvable, meaning they cannot be solved simply by using the usual method of iterating on individual rows and columns. When no further progress can be made, the algorithm has to test different alternatives in order to reach a solution. That backtracking mechanism is shown with tiles of varying colors:

("Mum" puzzle by Jan Wolter: https://webpbn.com/index.cgi?id=65)

Contributions

This project does not accept pull requests at the moment.

Please submit an issue for a feature request, a bug report or any question.

License