Photo mosaic maker

How a photo mosaic works

A photo mosaic is one large picture assembled from many small ones. From a distance you see the main photo; step closer and every patch turns out to be a separate picture — a holiday snap, a birthday, a pet. The effect works because the eye averages colour over an area, so a tile only has to be roughly the right colour for its place.

The maker splits your main photo into a grid and compares every cell with every tile photo. It does not just compare one average colour: each cell and each tile is measured in four quarters, so a tile that is dark at the bottom and light at the top lands where the main photo has the same gradient. Colours are compared in the Lab colour space, which follows human perception more closely than plain RGB values.

Two controls decide how clearly the subject comes through. Colour match lays the cell’s own colour lightly over each tile, and Show main photo blends the original in on top. Both make the motif easier to recognise; both also make the individual photos less visible. Somewhere between 10 and 30 per cent is usually the sweet spot.

Which photos work best

For the main photo, pick something with a clear subject and strong contrast — a face, a couple, a pet, a building against the sky. Fine detail such as small text or a busy crowd gets lost, because each tile can only carry one small patch of colour.

For the tiles, quantity and variety matter more than quality. With 50 photos a mosaic already works; with a few hundred it gets noticeably better, because there is a suitable tile for more cells. Photos in many different colours and brightness levels help, too: if all your tiles are beach pictures, the tool will struggle to find anything dark.

Avoid repeats spreads the tiles out. At a high setting the same photo is not placed next to itself and each photo is used roughly as often as the others. If you only have a handful of pictures, lower it — otherwise the colours suffer. Without any tile photos at all, the main photo itself is used as the tile, tinted to each cell’s colour: a simple effect, but a quick way to see how the layout looks.

Size, print and sharpness

The mosaic can be saved with a long side of 2000, 4000, 6000 or 8000 pixels. For the screen and social media, 2000 to 4000 is plenty. For print, count on about 300 pixels per inch for something viewed up close: 6000 pixels give about 50 cm, 8000 about 68 cm. A poster that hangs on a wall and is looked at from a metre away gets by with half that density, so 8000 pixels stretch to well over a metre.

The number of tiles decides how fine the picture is. Forty tiles across gives large, clearly visible photos and a rougher subject; a hundred gives a sharper subject with tiny photos. Click the preview to look at the tiles up close before you export.

On phones the size is capped automatically. Mobile browsers — Safari on iPhone and iPad in particular — refuse canvases above about 16.7 million pixels, which is around 4000 × 4000. The download button always shows the size you will actually get.

Why nothing is uploaded

A photo mosaic usually means handing over a whole album: family pictures, children, holidays. Most online mosaic makers need every one of those photos on their server. This tool does the matching and the drawing on your device — the photos are read by your browser, processed there, and never sent anywhere.

That also means no account, no watermark and no paid high-resolution version. The full-size file is the same one you see in the preview, only larger. Once the page has loaded, the tool keeps working even without a connection.