Nonogram Maker (Picross from a Picture)

What it is for

A nonogram (also called picross, griddlers or hanjie) hides a picture in a grid. The numbers beside each row and above each column give the lengths of the filled blocks in that line, in order; solving them reveals the picture. This tool makes printable nonograms from a built-in picture, from your own drawing with # and ., or from a PNG image, and adds an answer page.

The important part is the check. A nonogram can easily have two solutions, or need guessing. The tool solves the puzzle line by line like a person would; if that settles every cell, the solution is unique. If not, it can add given cells — printed pre-filled, or crossed out — until it solves without guessing.

Worked example

The built-in cat is 11 × 11 with 77 filled cells. Its first row clue is "1 1" (the two ear tips) and the fourth row is "11" (a full line). The result says "solvable line by line, so it has exactly one solution", with 0 givens.

Your own 8 × 8 smiley drawing cannot be solved line by line: the summary reads "2 given cells make it solvable line by line" and the warning repeats it. Those two cells are printed in grey on the puzzle page.

The rocket with automatic givens turned off shows what happens without the fix: "not solvable line by line", with a warning that it may have more than one solution.

A 5 × 5 checkerboard solves at once — every line clue is "1 1 1" or "1 1", and the crossings leave no choice.

How to read the result

• rowClues and colClues are the printed numbers; solution is the picture, one text row per grid row.
• lineSolvable tells you whether the picture works without help; givens is the number of cells the fix revealed.
• filledCells helps judge difficulty: very full or very empty pictures are easier.
• The PDF has the puzzle page and the answer page; SVG and PNG show the first page.

Tips and common mistakes

• Simple shapes with clear outlines make the best puzzles. Photos usually turn into noise; use the image option for logos, icons and silhouettes.
• For images, set Columns and Rows (2–50) and the Darkness threshold: cells darker than it are filled. Transparent pixels count as white; Invert fills the light parts instead.
• Keep Add givens until it solves line by line on for printed puzzles — a puzzle with two answers is frustrating.
• Thick lines every five cells help counting on paper.
• Large grids (30 × 30 and more) print small on A4; choose A3 or fewer cells.

FAQ

What does "line by line" mean?

For each row and column, the tool finds the cells that are filled (or empty) in every arrangement of the blocks that fits what is already known, and repeats until nothing changes. It never guesses.

Can I solve it on screen?

Yes. In Printshop press Play on screen…: click or press Enter to fill, right-click or press X to cross out, then check.

Are coloured nonograms possible?

Not yet; nonograms are black and white.