How to make a paint-by-numbers mural your whole class paints together

Classkraft turns one photo into a classroom paint-by-numbers mural. It reduces the image to a few flat colours, traces them into numbered regions, and splits the result across A4 sheets that students colour by hand and tape back into one large mural. Nothing is uploaded — the whole process runs in your browser.

How do I turn a photo into a paint-by-numbers mural for my class?

In Classkraft the mural workflow is five steps, and it produces print-ready PDFs at the end:

1. Pick a photo. Drag any PNG or JPG onto the dropzone.
2. Choose the number of colours — between 2 and 16, with 5 as the starting point. Fewer colours means simpler shapes and fewer paints to buy.
3. Choose the number of tiles — up to 200. One tile per student is the usual choice; two each makes a bigger mural with the same class.
4. Generate. Classkraft quantizes the photo to flat colours, traces the regions to vectors, slices them into tiles, numbers each region, and lays the tiles out on A4 pages.
5. Print and hand out. Each student gets their sheet, the numbered legend tells them which colour goes where, and the assembly map shows how the finished sheets fit together.

How do I print something bigger than one A4 sheet?

Both of Classkraft's modes solve the same problem — a picture larger than the printer — in two different ways. The mural mode tiles the traced, numbered artwork so students colour it in. Poster mode skips all recolouring and simply cuts an image into a grid of A4 sheets that tape back together into one large print. A 3-across by 2-down grid gives roughly 55 × 54 cm; the grid goes up to 8 by 8. Both modes print the same cut flaps, cut border and assembly map, so the taping step works identically whether or not anyone paints.

Are the photos uploaded anywhere?

No. Classkraft has no server and no account. Every stage — colour reduction, vector tracing, tiling, page layout and PDF rendering — runs on your own device in a Web Worker, and the source photo never leaves the browser. This is the part that matters if you are photographing children: there is no upload to consent to, no sign-in, and no analytics. The only things Classkraft stores are your light/dark theme preference and your chosen language, both in your browser's local storage. The full detail is in the Privacy Policy.

Is Classkraft free, and do I need an account?

Classkraft is free, with no account, no sign-in, and no watermark on anything it produces. There is no paid tier holding back resolution or features — the PDFs you get are the full-quality PDFs. The interface is available in English, German, Polish and Spanish. Classkraft also installs as a progressive web app: once installed it runs offline, which is worth doing if your school's wifi is unreliable on the day you need to print.

What kind of photo works best?

Classkraft works from flat colour, so the photos that trace cleanly are the ones already close to poster art: high contrast, bold shapes, few gradients, and colour spread across the whole frame rather than one large flat background. Busy photographs with soft lighting produce many small regions that are fiddly to paint. If a region comes out too small to colour, raise the detail-level setting, which sets the minimum region size, or reduce the number of colours. The in-app Prompt guidance panel gives a tested prompt for generating a suitable source image if you would rather make one than find one.