Making a sheet from your own picture

Add a photo. Drop it on the box, browse for it, or press the sample button to see how the tool behaves first.
Set the number of colors. The slider runs from 4 to 20. Ten is the starting point.
Choose a detail level. Easy, Medium and Detailed change how finely the picture is divided and how small an area is allowed to be.
Print it, or color it on screen. Print gives you the outline with numbers and a legend underneath. Download SVG gives the same sheet as a file that stays sharp at any size.

Everything is recalculated as soon as you move a control, usually in well under a quarter of a second, so it's worth trying a few combinations before you print.

What the settings actually do

To give you a feel for it, here's what one test photo (a close shot of autumn maple leaves, all yellows, oranges and rusty reds) produced with 10 colors requested:

Detail	Areas to color	Colors kept
Easy	78	9
Medium	159	10
Detailed	398	10

Notice that Easy kept only 9 of the 10 colors. After the picture is split into colors, any patch smaller than the minimum size for that detail level gets absorbed by its largest neighbor. If every patch of one color was tiny, that color disappears and the legend is renumbered so there are no gaps.

The same thing happens when you ask for more colors than the picture really has. A tiger-stripe pattern we tested is essentially cream, orange and black with soft edges, so even at 10 colors it came out with 4 or 5. Two near-identical blacks are folded into one rather than giving you a "9" and a "10" you couldn't tell apart with real pencils.

Rough guidance from testing:

Children, or a relaxed half hour: Easy with 6 to 8 colors. Expect somewhere between 20 and 80 areas, big enough for chunky crayons.
Adults with colored pencils or markers: Medium with 10 to 12 colors.
A long project, fine felt tips or paint: Detailed with 14 or more colors. Several hundred areas is normal, and the smallest ones get small numbers.

Which photos work best

The method is simple: every pixel is assigned to its nearest palette color, stray pixels are tidied up, and each connected patch becomes one numbered shape. That makes some pictures far better candidates than others.

Good choices:

A single clear subject against a plain or blurred background: a pet, a flower, a mug, a face lit from one side.
Strong, separate colors. Fruit, toys, beach huts, a sunset over water.
Clear light and shadow. A side-lit portrait turns into recognizable planes of light and dark, which is the look people expect from a paint by number kit.

Poor choices:

Busy, fine texture such as grass, gravel or a crowd. These turn into hundreds of crumbs.
Very low contrast like fog, snow or a beige room. There isn't enough difference to split into areas.
Tiny faces in a group photo. Crop to one or two people first; any phone's editor will do.

Cropping helps more than any setting. The sheet always uses the whole frame, so a subject that fills most of it gets most of the detail.

Printing tips

The Print button opens your browser's print dialog with only the sheet on the page: the outline, the numbers and a key showing each color's swatch and HEX code. It is scaled to fit one page. A few things make the result better:

Turn on background graphics in the print dialog if the swatches in the key come out blank.
Print the outline in black and white and keep the key on screen if you want to save ink. The outlines are mid-gray on purpose so they disappear under light colors.
For anything larger than A4 or Letter, use Download SVG. It's a vector file, so a print shop or a poster-printing site can scale it up without blur.
Want to check your work afterward? Switch to Show finished picture and keep the screen next to you.

Coloring it online

Pick a number from the palette under the picture, then click or tap the areas with that number. Tap a filled area again with the same color to empty it. The line below the picture counts how many areas you've done and how many match their number, and says "Finished!" when every one is right. Show finished picture reveals the answer at any point; Clear my coloring starts again.

Your coloring lives only in this tab. Reloading the page or changing a setting resets it, because a new setting produces a new set of areas.

Matching real paints and pencils

Each color in the key has a HEX code. Pencil and marker sets rarely contain those exact shades, so match by eye from the swatch, or paste a code into the color mixer to see roughly how to mix it from a few paints. If two colors in the key look too alike for your set, generate the sheet again with fewer colors rather than guessing.

Honest limits

Shapes follow a grid of cells, so edges have small steps instead of smooth curves. They're easy to color over, but don't expect the smooth outlines of a printed kit.
The palette comes only from your photo. The tool can't suggest a more pleasing scheme or swap colors for you; for that, recolor the photo first with the image color changer.
Very small areas sometimes carry tiny numbers. Choose a simpler detail level if they're hard to read.

The picture you add stays on your device: the whole conversion runs in the page, and nothing is sent to a server.