Colouring page maker
Turn a photo into a colouring page
Clean black outlines from any picture: the family dog, a favourite toy, the view from a holiday. Adjust the detail and line thickness, then print. The photo never leaves your device.
11 lines · A4 portrait · 0.7 mm lines
Sample: Hot-air balloon
Drop a photo here or paste one. JPG, PNG, WebP, GIF or SVG.
From photo to colouring page
- Start with a sharp photo in which the subject stands out from the background. Toys, pets, cartoons and buildings give the clearest lines.
- Detail sets how much the photo is blurred first: Simple keeps the main shapes, Fine keeps fur and leaves.
- Sensitivity sets how faint an edge may be and still become a line. Remove specks drops short scraps, and Close small gaps joins line ends that almost meet, so areas are easier to colour inside.
- Pick a thickness: about 1 mm for small hands and crayons, 0.4–0.6 mm for felt-tips and older colourists.
How the lines are found
The photo is shrunk to 800 pixels and converted to CIELAB, so a border between two equally bright colours still counts. Canny edge detection blurs the picture, measures how fast the colour changes, thins every edge to one pixel and keeps the strong edges plus any weaker ones that continue them. The edges are thinned again with the Zhang–Suen method, joined into lines, smoothed and simplified with the Douglas–Peucker algorithm, then drawn at the thickness you chose, so they stay crisp at any print size.
Sources
- Canny J. A computational approach to edge detection. IEEE Transactions on Pattern Analysis and Machine Intelligence 1986;PAMI-8(6):679–698. doi:10.1109/TPAMI.1986.4767851
- Zhang TY, Suen CY. A fast parallel algorithm for thinning digital patterns. Communications of the ACM 1984;27(3):236–239. doi:10.1145/357994.358023
- Douglas DH, Peucker TK. Algorithms for the reduction of the number of points required to represent a digitized line or its caricature. Cartographica 1973;10(2):112–122. doi:10.3138/FM57-6770-U75U-7727
- CIE. Colorimetry, 4th edition (CIE 015:2018), for the CIELAB colour space. doi:10.25039/TR.015.2018
Questions
Why are some lines doubled?
A thin dark detail such as a whisker or a mast has an edge on each side, so it becomes two close lines. Simple detail or a thicker line merges them; children can also simply colour the gap in.
The page is full of little lines. What helps?
Lower the sensitivity, choose Simple detail and raise Remove specks. Busy backgrounds cause most clutter, so crop the photo first so the subject fills the frame.
Is my photo uploaded?
No. The edges are found by a background worker in your own browser, and the photo is never sent anywhere or saved.