Online Image Posterize Tool
Reduce levels per color channel. Processing takes place locally in your browser.
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What this tool actually does
Color levels numeric field has displayed bounds 2 to 32, default 6. The level count applies independently to each RGB channel, not to the total number of image colors.
Checkable behavior
For q levels, step=255/(q-1); each channel becomes round(channel/step)*step, then byte-rounded. Example 6 levels gives step 51: RGB(100,160,240) becomes RGB(102,153,255).
Controls, output and limitations
Six levels per channel allow up to 216 RGB combinations, not exactly six colors. The image may use fewer combinations. Two levels can yield up to eight combinations; this is not a black-and-white threshold tool.
Browser-local single-image preview and download. Useful for flat poster-like color regions; gradients can show bands. No adaptive palette, dithering or exact file-size guarantee. Keep the original.
The color-count examples refer to opaque RGB pixels. The filter leaves alpha unchanged, but browser storage and PNG export can round RGB values in transparent pixels. This is not a guarantee of a fixed palette size or an indexed PNG.
Processing takes place locally in your browser.