Posterize an image

How it works

Tap or click the box to choose one or more images, pick the number of tones and press "Posterize". Each pixel's red, green and blue values are rounded to the nearest of the evenly spaced tones you chose. Example: with 4 tones each channel can only be 0, 85, 170 or 255, so a red value of 180 drops to 170. A photo with thousands of colours ends up with at most 64, and smooth gradients become stepped flat areas. With "Greyscale" the photo is first turned grey and then rounded the same way; 3 tones give a three-layer stencil of black, mid-grey and white. The result line reports how many colours are left. The output is PNG and everything runs in your browser.

This tool is also known as posterize image, posterize photo online, reduce colors in image, poster effect, photo to stencil, stencil maker, pop art effect.

What is Posterization?

Posterization reduces the smooth colour transitions in an image to a handful of flat tones. The name comes from old printed posters made with only a few inks: each colour needed its own plate, so there were no in-between shades. Digitally, the values each colour channel may take are limited. The result resembles comics, pop art or screen printing, and gradient areas such as a sky show clear bands.

What is Stencil?

A stencil is a template cut from paper, vinyl or acetate that lets you spray or dab paint through it to repeat the same image. Each tone needs its own layer. That is why a stencil image should have very few tones: 2 tones mean one layer, 3 tones mean two. Cutting machines such as Cricut and Silhouette also trace flat-toned images into much cleaner cut lines.

Posterize vs. black and white: what is the difference?

Converting to black and white removes colour but keeps all 256 shades of grey, so transitions stay smooth. Posterizing reduces the number of tones: in colour mode the colours stay but drop to a few flat steps, in greyscale mode only 2 to 8 greys remain. In short, black and white throws away colour information, posterize throws away tonal detail. A cutting stencil needs both, and the "Greyscale" mode here does both in one step.

How many tones should I choose?

For pop art and a comic look, 3–4 tones in colour is a good start; skin tones split into a few flat areas. 6 and 8 tones stay close to the photo and only show bands in skies and shadows, which you can use on purpose for a vintage print feel.

For a cutting stencil choose greyscale with 2 or 3 tones. Two tones give one cut layer (black and white); a third tone adds a second layer for shadows. More than four layers are hard to cut by hand.

Why is the output always PNG?

JPG compression creates new in-between colours along the borders of flat areas. Save a posterized image as JPG and 8 colours turn into hundreds, and a cutting machine treats those edge smudges as separate shapes. PNG is lossless, so the colour count in the result note matches the file.

Flat areas compress well in PNG, so the file size usually stays reasonable. If the image is only for screens, you can convert the PNG to JPG afterwards and the poster look remains.

Frequently asked questions

How do I posterize a photo?

Choose the photo on this page, pick the number of tones and press "Posterize". The colours drop to the chosen number of flat tones; save the PNG with "Download".

How do I make a stencil from a photo?

Pick "Greyscale" with 2 or 3 tones and posterize. The black, grey and white areas are your separate cutting layers. Starting with a photo that has a plain background improves the result a lot.

Why is the colour count lower than the maximum in the option?

The maximum assumes every tone of every channel combines with every other (4 tones: 4×4×4 = 64). A real photo never uses most of those combinations; a sky photo, for example, has no red-green tones.

Can posterizing be undone?

No, the discarded in-between tones do not come back. The tool never touches your original; it creates a new PNG with "-posterized" added to the name, so pick the original again to try another number of tones.