Nonogram maker: you draw, the numbers follow

How to make a nonogram

1. Pick the size. Width and height are set separately, from 5 to 50 squares. A 10 × 10 or a 15 × 15 plays well on a phone.
2. Draw. Tap a square to fill it, slide to fill a run; go over a filled square to clear it. “Invert” swaps black and white.
3. Or start from a picture. Import it, paste it or drop it on the page: it gets shrunk to the size of the grid, then every square turns black or white by the threshold, which you adjust with the slider.
4. Read the verdict under the grid. It changes with every square.
5. Send it. Give it a name if you like, try it yourself, then “Send to a friend”.

Why some drawings don’t make good nonograms

The numbers only give the length of each run of filled squares, never its exact position. Two different drawings can therefore have exactly the same numbers, and the player has no way of knowing which one you meant. The textbook case fits in four squares:

■ ·     · ■
· ■     ■ ·

The maker hunts for these doubles while you draw. It first replays the grid like a player, line after line, without ever assuming anything. If it gets stuck, it looks for a second solution, then shows you the squares involved.

• Lone diagonals are the classic trap: two squares that only touch at a corner can often flip, as in the diagram.
• Isolated dots cost a lot. A single pixel in the middle of nowhere gives a “1” that says almost nothing about where it is.
• Solid areas help. An almost full row is deduced at a glance, and it unlocks every column it crosses.
• A clean edge beats a lacy outline: small notches are often ambiguous.

The button that fixes it

“Make it playable” shows up when the grid has several solutions, or when the deduction stalls. The maker tries flipping, one by one, the squares involved and their neighbours, keeps the one that unblocks the deduction the most, and repeats until the grid solves from start to finish. Your drawing moves by a square or two, rarely more: they are circled in red, and “Undo” puts them back.

From a picture to a grid

The picture is shrunk in steps down to the size of the grid, then every square turns black or white. The starting threshold is computed from your picture (Otsu’s method), the slider adjusts it, and the grid inverts itself if the picture comes out more black than white. Silhouettes, logos and icons give the best results; a holiday photo shrunk to 20 × 20 mostly gives noise, and will need touching up. The picture never leaves your browser.

Sharing your grid

“Send to a friend” opens your phone’s share sheet, or copies the link on a computer. The drawing and its name are kept on our server for a year, under an eight-character id: that is what keeps the link short, and what lets the game tell you when your friend has solved it. Your friend opens it in the Nono game, and only sees the numbers. They fill, cross out, can ask for a hint that names the line to look at, and only find out what your drawing is once the grid is solved, otherwise it would give the answer away.

“Printable image” makes a PNG of the empty grid with its numbers, without the name. To solve a grid you found elsewhere, the nonogram solver even reads a photo; to learn the method, the guide to solving nonograms starts from the overlap rule.

Frequently asked questions