Nonogram (Picross)

Nonograms (also called Picross or Hanjie) are logic puzzles in which you fill in cells using the numbers written beside each row and column to reveal a hidden picture. Each number is the length of a run of consecutive filled cells in that line; when a line has several numbers, the runs appear in that order with at least one empty cell between them. For example, 3 2 in a 10-cell line means three filled cells, a gap, then two filled cells. When every row and column matches its clues, the picture appears and the puzzle is done.

1) Overlap the big numbers. If a 15-cell line has a 9, the middle three cells (7th to 9th) are filled whether the run sits at the far left or the far right. The closer the sum of the clues plus the minimum gaps is to the line length, the more cells are settled at once.

2) Cross out zero lines. A line whose clue is 0 has nothing to fill, so mark the whole line with X, and mark cells that cannot be part of any run. X marks are only notes and never affect the check.

3) Alternate between rows and columns. Cells settled in one line give new information to the lines that cross it. When you get stuck, scan the lines whose clues are not yet dimmed. A finished line dims its clue numbers to show you where to look next.

4) Controls. There are three tools: O ▲ X. O fills a cell (in a color puzzle it paints with the color picked in the palette), ▲ is a note for cells you are unsure about, and X marks a cell as empty. Click a cell to mark it with the selected tool, and click the same mark again to clear it. The right mouse button always places an X. X and ▲ count as empty when the puzzle is checked, so they can stay on the board; the puzzle is solved as soon as the filled cells match the clues. Drag to apply the same action to several cells, and use Undo to step back one action at a time. On desktop, the row and column under the pointer are highlighted.

In color puzzles the clue numbers are shown as chips in their color. Each number is the length of a run in that color. Blocks of the same color need at least one empty cell between them, but blocks of different colors may touch. For example, a red 2 followed by a blue 3 may sit directly next to each other. Choose the color to paint with the swatches in the tool row, use ▲ and X exactly as in black and white, and the picture is revealed when every row and column matches its colored clues. Records for color puzzles are stored separately from black-and-white records of the same size.

With Color (the default), the photo is reduced to 2 to 6 colors to make a color puzzle. The lightest color becomes the background (empty cells), so photos with a light background work best. With Black & white, the threshold slider decides from which brightness cells are filled (it starts at the Otsu value); leave it as is when the subject is dark on a light background, and turn on Invert for the opposite. If fewer than 5% or more than 95% of the cells are filled the puzzle is no fun, so adjust the settings.

High-contrast, simple pictures work best. Silhouettes on a clean background, logos, characters, and lettering keep their shape even on a small grid, while landscapes with smooth color transitions tend to turn into blotches when reduced.

The image is reduced to any width and height you choose (at least 5 cells). With the default Keep original aspect ratio on, the height follows the width in the photo's proportions; with it off, the picture is center-cropped to the width:height ratio you set. More cells keep more detail but take much longer to solve. A picture larger than 64 cells on either side is too hard to solve on screen, so it can be saved as a printable PNG or PDF instead of played.

A puzzle with the "Solvable by logic" badge can be solved without guessing. With "Needs guessing" you may have to try a cell, and there may be more than one solution. For very large grids the check is skipped. This tool accepts any grid in which every row and column matches its clues, even if it differs from the original picture.

Uploaded images are never sent to a server and are processed only in this browser. Your records and the list of solved puzzles are stored only in this browser (localStorage). A link made with "Copy puzzle link" contains only the grid after the # in the address (one bit per cell for black and white; the palette and a color number per cell for color), never the original photo.

The black-and-white 10 to 30 cell stages are Google Material Symbols (Apache License 2.0), and the color stages are Google Noto Emoji (Apache License 2.0), converted into grids with a reduced color count; the black-and-white 5×5 puzzles are hand-drawn. Full license texts: LICENSE-material-symbols.txt · LICENSE-noto-emoji.txt