Nonogram Generator (Picross)

Nonogram Generator (Picross) - Create Solvable Picture Logic Puzzles from Any Image

What Is a Nonogram?

A Nonogram (also known as Picross, Griddlers, Paint by Numbers, or Hanjie) is a picture logic puzzle where you fill cells in a grid to reveal a hidden image. The puzzle provides numerical clues for each row and column that describe the lengths of consecutive filled cells in that line. By cross-referencing row and column clues, you logically deduce which cells should be filled and which should remain empty.

Nonograms were independently invented by Non Ishida, a Japanese graphics editor, and Tetsuya Nishio, a professional puzzler, in 1987. Ishida won a design competition in Tokyo using a grid puzzle concept that would become the Nonogram. The puzzle format gained massive popularity in Japan through puzzle magazines, and later spread worldwide. Nintendo brought the format to gaming audiences as "Picross" through a series of popular Game Boy and DS titles that have sold millions of copies.

How Nonogram Clues Work

• Row clues: Numbers listed to the left of each row describe groups of consecutive filled cells from left to right. For example, "3 1 2" means there is a group of 3 filled cells, then at least one empty cell, then 1 filled cell, then at least one empty cell, then 2 filled cells.
• Column clues: Numbers listed above each column describe groups of consecutive filled cells from top to bottom, following the same logic.
• Zero clue: A clue of "0" means the entire row or column has no filled cells at all.
• Gaps are mandatory: Between any two groups of filled cells in the same row or column, there must be at least one empty cell.
• No guessing needed: A well-designed Nonogram can be solved entirely through logic without trial and error.

Solving Strategies

• Overlap method: For a line of width W with a clue of length L, the overlap region (L - (W - L)) cells in the middle can be filled immediately when L is more than half of W.
• Edge logic: If the first clue starts at the edge of a row, you know exactly where the first group begins. The same applies to the last clue at the opposite edge.
• Marking empty cells: Once you know a cell must be empty, mark it with an X. This constrains neighboring clue groups and accelerates deduction.
• Cross-referencing: Always check both the row and column clues for each cell. A cell that must be filled by row logic and confirmed by column logic is guaranteed.
• Full-line completion: When a row or column has all its filled cells placed, mark all remaining cells as empty.

How To Use This Generator

• Upload your own image (PNG, JPG, WEBP, or GIF) or choose a built-in demo pattern.
• Set grid width and height (5 to 45). Start with 12-20 for beginner-friendly puzzles.
• Adjust the dark pixel threshold to control how many cells become filled.
• Choose "Contain" to preserve the full image shape, or "Cover" to crop and fill the grid.
• Enable invert if the puzzle appears too sparse or too dense.
• Download the puzzle PNG for solving, answer PNG for checking, and clue text for printing.

Tips for Clean Puzzles

• High-contrast images with clear silhouettes produce the best puzzles.
• Simple icons and logos work better than complex photographs.
• A fill density between 25% and 55% typically produces the most enjoyable solving experience.
• If using photos, try smaller grids (15x15) to avoid excessive detail that obscures the picture.

Nonogram Variants

• Color Nonograms: Use multiple colors instead of just black and white, with separate clues for each color.
• Triddlers: Nonograms on a triangular grid with three sets of clues instead of two.
• Multi-grid Nonograms: Several smaller puzzles that combine to form one large picture.

Frequently Asked Questions

Can I generate Nonograms from photos?

Yes. Photos usually need more threshold tuning than icons or logos. Start at 18x18 and adjust threshold until the shape is recognizable.

What is a good fill density?

Most playable puzzles fall between 25% and 55% filled cells. Extremely low or high density reduces solving quality and enjoyment.

Do I need to solve online?

No. Download the puzzle PNG and clue sheet, print them, and solve with pencil or marker on paper.

Does every generated puzzle have one solution?

Every puzzle is checked with row-and-column logic. If the picture alone would have more than one answer or need guessing, the generator pre-fills the fewest given cells it can find, shades them on the puzzle and lists them in the clue text, so the puzzle can be solved by logic alone.

Can I adjust the threshold without uploading again?

Yes. Under the result, the Fine-tune threshold slider and Invert box redraw the puzzle, answer, clues and downloads instantly from the same picture, and carry the value into the form for your next run.

What grid size is best for beginners?

Start with 10x10 to 15x15. These sizes produce shorter clue lists and faster solving times while still forming recognizable images.

What kind of image makes a good picture for a nonogram?

Choose a simple image with a clear silhouette and strong contrast between the subject and its background. A dark object against a light background, such as a black cat shape on white, is easier to represent in filled and empty cells than a detailed photo with many similar tones. Fine details and thin lines may disappear when reduced to a grid. Cropping to the main subject can help the resulting puzzle remain recognizable.

Why does a detailed photo look different when it becomes a nonogram?

A nonogram reduces an image to a grid of filled and empty cells, so small features and gradual shading cannot be preserved as they appear in the original. For example, a 10-by-10 grid has only 100 cells to represent the whole picture. Details narrower than a cell may vanish, while areas with similar brightness can blend together. A simple, high-contrast image usually produces a clearer puzzle than a busy photo.

How do I make a nonogram easier to solve from an image?

Start with a simple image and a smaller grid so the picture has fewer cells and the clue lines are easier to work through. For example, a bold icon with a few large shapes is easier to translate into row and column groups than a detailed landscape. Look for images whose filled areas form clear blocks rather than thin scattered marks. This is general puzzle-design guidance; the page’s available image and grid settings determine the exact result.

Learn More

• Nonogram rules and history
• Binary image basics for thresholding