Pixelate Image

Pixelating turns a picture into large square blocks of colour. It is used for retro and mosaic effects, for teaser images, and for blurring out a whole picture so only its rough shapes and colours remain. Set the block size in pixels or say how many blocks you want across, choose average or centre sampling, and optionally reduce the colours. The image keeps its original dimensions, and the work happens in your browser.

How to use this tool

1. Choose one or more images.
2. Set the block size in pixels, or the number of blocks across the width.
3. Choose average sampling for a smooth mosaic or centre sampling for a sharper, higher-contrast look.
4. Optionally reduce to 8–32 colours, then download.

Formula

block colour = Σ(colour × alpha) ÷ Σ alpha over the block; block count = ceil(width ÷ b) × ceil(height ÷ b)

b is the block size in pixels; with "blocks across" it is round(width ÷ blocks). Averaging is weighted by transparency so see-through pixels do not darken the colour. Centre sampling copies the pixel at the middle of each block instead. Colour reduction groups the block colours into a palette with a pairwise-nearest-neighbour quantiser and snaps every block to the nearest palette colour.

Example

A 1200 × 800 photo with 20 px blocks becomes a mosaic of 1200 ÷ 20 × 800 ÷ 20 = 60 × 40 blocks, still 1200 × 800 px. Asking for 40 blocks across gives a block size of round(1200 ÷ 40) = 30 px and 40 × ceil(800 ÷ 30) = 40 × 27 blocks; the last row is only 20 px tall.