Pixelate Image

What pixelation actually does

Pixelation divides the image into blocks and replaces each block with a single average colour, so nearby pixels genuinely stop existing as separate values. That is meaningfully different from a blur, which averages colours while keeping the underlying variation partly recoverable, and it is why a mosaic is a stronger obstruction. It is also not deletion: the information is gone from the pixels but the fact that something was there remains, and with the original image the average can in principle be approached and the region guessed.

NotePixelation is a stronger obstruction than blur but still not deletion.

Block size is the whole decision

A small block leaves the image recognisable, which is what a stylised mosaic effect wants. A large block makes the region unreadable, which is what obscuring a face needs. The choice also affects how the image reads overall: very fine blocks create a deliberate retro mosaic look, medium blocks look like a deliberate stylisation, and a handful of enormous blocks on a large image looks like a broken file rather than an effect. For privacy, the block has to be large relative to the feature being hidden, which is why a small block over a face hides nothing.

• Small blocks: a deliberate mosaic or retro effect, image stays recognisable.
• Medium blocks: a clear stylisation.
• Large blocks: unreadable, which is what privacy requires.
• Blocks must be large relative to the feature being hidden.
• Very large blocks on a big image look like a rendering error.

NoteTo actually obscure a face, the block has to be large relative to the face. Fine blocks hide nothing.

Mosaic as a design effect

Pixelation has a legitimate place in design. A fine mosaic over a photograph gives a texture that reads as contemporary and is used constantly in poster and album artwork. Applied as a gradient, fading from fine to coarse or from clear to fully pixelated across the frame, it directs the eye and looks deliberate where a uniform mosaic can look like a compression error. A single accent region, such as a face, works as a focal treatment. The difference between a good mosaic and a bad one is intent and variation.

• A fine mosaic over a photo gives a modern texture. Common in poster design.
• A gradient from clear to pixelated directs the eye and looks deliberate.
• A single accent region, such as a face, works as a focal treatment.
• A uniform coarse mosaic can look like a compression error.
• Vary the block size across the image to make the effect read as intentional.

What pixelation is not good for

It is not a security measure and should not be used as one. Faces obscured by a mosaic have been recovered from blurred images more than once, and the same techniques apply more readily to pixelated ones, because the block average is a direct summary of the region. If something must genuinely not be identifiable, because it is a face of someone who did not consent, a licence plate, a house number, or a document, the correct action is to cover the region with something solid or to crop it out. Obscuring is not the same as deleting, and treating it as though it were is the mistake worth avoiding.

• A mosaic is not a security measure and does not reliably hide a face.
• Recovery techniques that work on blur also work on pixelation.
• For anything that must not be identifiable, cover it or crop it out.
• Obscuring is not deleting, and the distinction matters.
• If someone did not consent to appearing, remove them rather than obscuring them.

NoteIf a face must not be identifiable, remove it. Do not obscure it.