Photo mosaic maker

How to make a photo mosaic

1. Pick the main picture. A face, a couple or a pet with clear light and dark areas works best; busy, low-contrast pictures turn to mush at 40 tiles across.
2. Add the tile photos. Pick 20 to 1,000 photos, or a whole folder on a computer. Each is shrunk to a 128 px thumbnail as it is read, and the page shows how much memory the set takes. Tick Keep these photos to find them again next time.
3. Set the grid and the print size. Choose the tiles across (20 to 150), square or 4:3 cells, and the print size in cm or inches. The main picture is cropped from the centre to that shape.
4. Make it, then tune it. Press Make mosaic. Limit how often a photo is used and how close repeats may sit, switch on 2 × 2 detail for sharper edges, and use the colour blend if the picture does not show through. Pinch or scroll to zoom; fade the main picture over the preview to compare.
5. Download. Download JPEG saves the mosaic at the print size and DPI you set. CSV map saves a list of which photo sits in each row and column, made on this device.

What it cannot do

• It only uses the photos you give it. With too few it repeats them: a 40 × 53 grid has 2,120 cells, so 100 photos are each used about 21 times. The page shows how many your grid needs.
• No AI. It matches colours; it does not recognise faces or invent tiles, and it cannot make a picture show through photos that are all the same colour.
• It does not order prints. It makes the file; you take it to a print shop or an online printer.
• Very large exports are slow on a phone, and above 16 megapixels a phone gets the mosaic in parts. Tiles are drawn from 128 px (or 256 px) thumbnails, so a tile printed larger than that looks soft; the page warns when that happens.
• Photos are not kept unless you ask. Without Keep these photos, reloading the page forgets them. HEIC photos open only in browsers that read HEIC (Safari does; most others do not) and are skipped elsewhere, with a count.

How the matching works

The main picture is divided into the grid. For each cell the page works out the average colour in OKLab, a colour space where equal distances look about equally different to the eye, and it does the same for the visible (centre-cropped) part of every tile photo. Each cell then gets the closest photo that obeys your rules. With 2 × 2 detail on, the four quarters of a cell are compared with the four quarters of each photo, so a photo that is dark on its left half goes where the main picture has a dark left edge.

Never repeat within 2 cells means the same photo is never placed in the 5 × 5 block around itself, so it needs at least 9 different photos (16 for 3 cells, 36 for 5). When the rules cannot all hold, the closest photo is used anyway and the page tells you how many cells that happened in.

Colour blend tints each photo toward the colour of its cell: at 20 % every pixel moves a fifth of the way. It makes the main picture much easier to see from across a room, at the cost of the photos looking less like themselves. At 0 % every photo is untouched.

For a poster seen from a metre or more, 150 to 200 DPI is plenty; 300 DPI matters for small prints held in the hand. Count on the tiles: 40 tiles across a 40 cm print makes each tile 1 cm wide, which at 200 DPI is 79 px, well within a 128 px thumbnail.

Questions

Is there a free online photo mosaic maker that does not upload my photos?

Yes, this one. The main picture and every tile photo are opened by your browser and shrunk to small thumbnails inside this page; none of them is sent to a server. There is no account, watermark or fee, and the JPEG you download is full size.

Do I need to download a photo mosaic app?

No. It runs in the browser on a phone, tablet or computer. On a computer you can pick a whole folder of photos at once; on a phone you pick them from the photo library. If you tick Keep these photos, the thumbnails stay in the browser's storage on this device so you can come back without picking them again.

Does this photo mosaic maker use AI?

No. It measures the average colour of every grid cell of your main picture and of every tile photo, and puts the closest-coloured photo in each cell, with your rules about repeats. Nothing is generated or invented: every tile is one of your photos, and with the blend at 0 % they are not even recoloured.

How do I get a photo mosaic printed near me or in the UK?

Set the print size the shop offers (for example 50 × 70 cm or 16 × 20 in) and 200 or 300 DPI, download the JPEG, and upload that file to any photo printer or take it to a local print shop. The page shows the pixel size, for example 50 × 70 cm at 200 DPI is 3,937 × 5,512 px. Above 16 megapixels it saves the picture in parts that line up edge to edge; print shops usually want one file, so make that export on a computer with the one-file option.

How many photos do I need for a photo mosaic?

At least 20, and more is better. A grid 40 tiles across a portrait print has about 2,400 cells, so 200 photos are each used about 12 times. With the rule never within 2 cells of itself you need at least 9 different photos for that rule to hold everywhere; the page tells you what your grid needs as you change it.