Nonogram / Picross Solver (Tkinter)

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A local desktop Nonogram (Picross) solver with a Tkinter GUI. Enter row and column clues, solve using logic propagation plus backtracking, and save/load puzzles as JSON. Designed for Python 3.10+ with no third-party dependencies.

The vast majority of the code was generated by GPT.

Features

• Board-first workspace with a dedicated header, live sidebar, and activity trail
• GUI for editing row/column clues and visualizing the grid
• Scrollable board area so larger puzzles do not crush the layout
• Live puzzle summary with dimensions, clue balance, and solve telemetry
• Left-click cycles a cell through unknown/filled/empty, right-click sets empty
• Logic propagation (constraint intersection) + DFS backtracking
• Detects no-solution / unique-solution / multiple-solution cases
• Step mode: one propagation pass for incremental solving
• Stop button to cancel long solves (threaded, UI stays responsive)
• JSON open/save with current grid state

Requirements

• Python 3.10+
• Tkinter (ships with standard Python on most platforms)

Quick Start

python main.py

Optional: open the sample puzzle at examples/sample_10x10.json.

UI Guide

The interface is organized into three regions:

• Header bar for project actions, solver actions, and zoom control

• Left sidebar for puzzle stats, legend, and live solver telemetry

• Main workspace for the board, status banner, and activity trail

• New: create a new puzzle size

• Open/Save: load or persist a JSON puzzle file

• Solve: full solve (propagation + DFS), reports status

• Step: one propagation pass (no backtracking)

• Stop: cancel a running solve

• Reset: clear the grid to all unknown

Editing clues

• Double-click a row/column hint area to edit that line.
• Use . (dot) as the separator when typing clues, for example:
  • 3.1.2 means blocks of 3, 1, and 2
  • empty input means no filled cells
• Dot separators are used to make numeric keypad input faster.
• Display formatting uses spaces (rows) or line breaks (columns); dots are input-only.

Grid interaction

• Left-click cycles unknown (-1) -> filled (1) -> empty (0)
• Right-click sets empty (0)
• Mouse wheel scrolls the board when needed
• Ctrl + mouse wheel adjusts board zoom

Solver Notes

The solver works in two phases:

1. Logic propagation

   • For each row/column, generate all line patterns that match the clue.
   • Filter patterns against current known cells.
   • Intersect all valid patterns to determine forced cells.

2. Backtracking (DFS)

   • If propagation stalls, choose the row/column with the fewest candidates.
   • Branch on candidate patterns, continue propagation.
   • Stop after finding two solutions to report "multiple solutions".

Solve can be interrupted at any time with Stop.

Step vs Solve

• Step runs exactly one propagation pass: it generates valid line patterns for all rows and columns, intersects them, and applies any forced cells.

• Solve repeats propagation until it cannot make further changes, then switches to backtracking search. It chooses a row/column with the fewest valid candidates, branches on a candidate, and continues propagation in each branch. The search stops after 2 solutions to report "multiple solutions".

  

JSON File Format

{
  "width": 10,
  "height": 10,
  "row_clues": [[3], [1,1], [], ...],
  "col_clues": [[2], [1,1], [], ...],
  "grid": [[-1, -1, 1, 0, ...], ...]
}

Grid values:

• -1 = unknown
• 0 = empty
• 1 = filled

Project Structure

nonogram/
  __init__.py
  model.py   # data model + JSON IO
  solver.py  # propagation + backtracking solver
  gui.py     # Tkinter UI
main.py      # app entry point
README.md
examples/
  sample_10x10.json

Performance

• Typical 5x5 to 25x25 puzzles solve quickly.
• Hard puzzles may require deeper search; use Stop to cancel.

Exporting an Image

This project does not include a built-in PNG export. You can:

• Use a screenshot tool, or
• Add Pillow yourself and export from the canvas

Troubleshooting

• If Solve reports "no solution", verify the clues and current grid state.
• If Solve reports "multiple solutions", the puzzle is ambiguous.
• If it is slow, try Step to see propagation progress or Stop to cancel.