OneTaskBy Tim King · Updated
Posterize Effect
Cut Each Colour Channel to a Few Levels for a Screen-Print Look, With Dither
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How the Posterize Effect works
This posterize effect reduces each colour channel of a photo to a handful of levels, so smooth gradients break into flat bands of colour. The result looks like a screen print, a vintage travel poster or a comic panel.
How the posterize effect works
Each of the red, green and blue channels normally has 256 levels. The tool rounds every value to the nearest of the levels you choose, spread evenly from black to full brightness. With four levels per channel the whole image uses at most 64 colours.
Choosing the number of levels
Two levels gives eight pure colours and a loud pop-art look. Three to five levels keep the subject recognisable with clear bands. Eight or more is subtle and mainly shows in skies and skin tones.
Ordered dither
Banding can look harsh in gradients. Ordered dither adds a fine Bayer pattern before rounding, which mixes neighbouring levels into a crosshatch texture that suggests in-between tones, like old computer graphics.
Private by design
Posterizing runs in your browser, and the photo is never uploaded.
FAQ
What does posterize mean?
Posterize means reducing the number of tones in an image so continuous shading becomes a few flat areas. The name comes from posters printed with a small number of inks, where gradients were not possible.
Is posterize the same as posterise?
Yes. Posterize is the American spelling and posterise the British one. Both describe the same effect, which Photoshop and GIMP list under Posterize in their adjustment menus.
How can I get specific poster colours?
Posterize keeps the photo's own colour mix. For a fixed palette, posterize first with two or three levels, then use the replace colour tool to swap each band for the colour you want.
Why does the output look noisy with dither on?
Ordered dither deliberately adds a regular pattern of light and dark pixels to fake extra tones. It looks smooth at a distance or when shrunk, but up close you will see the pattern.
See also: all Images tools, Audio, Video & Screen, PDF, SVG, Simulations & Screensavers, Generative Art, Chart Makers, 3D Model Viewers, Drawing Pads, Mockups & 3D Making, Diagram Makers, 3D Science, Tracker Music.
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