What is posterization?

Posterization (or "solarization" in some contexts) was originally a darkroom technique in which photographic prints were deliberately over-exposed to reduce tonal gradation. The name comes from the flat-color look characteristic of hand-printed posters.

Creative uses

Bold, graphic artwork and limited-color prints
Profile pictures and social media avatars with a stylized look
Reducing file size by decreasing unique colour count before exporting as GIF or 8-bit PNG
Preprocessing images for embroidery or screen-printing

How posterization works

Each color channel (R, G, B) is divided into N equal bands; all values within a band are rounded to that band’s representative value. For N = 4:

Input range	Output value
0–63	32
64–127	96
128–191	160
192–255	224

This is applied independently to each R, G, and B channel, reducing tonal gradients to flat bands of color.

Levels vs. posterization

The level count (N) controls how flat the final image looks. Fewer levels produces a more graphic, poster-like result:

Level 2: near-silhouette effect — each channel is either near-black or near-white.
Level 4: bold flat color areas with strong contrast.
Level 8: subtle banding that approaches the original image.

Post-processing tips

For the most graphic result, convert to grayscale first, then posterize — this eliminates color complexity and produces clean black-and-white bands.
Apply a slight Gaussian blur before posterizing to reduce noise artifacts; sharp noise becomes distracting blobs at low level counts.
Use error correction level H in the QR Code Customizer when including posterized images to ensure scanability.