Nirmion
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Image Tools / Local studio

Image Posterize

Reduce each still-image RGB channel to a chosen number of levels while preserving resolution, alpha, and browser-local privacy.

Runs locallyNo image upload to Nirmion

Step 1 / Source

Choose one image

JPEG · PNG · WebP · 20 MB

Drop your image here

Or browse for a JPEG, PNG, or WebP image that you own or are authorised to edit.

One file · up to 20 MB · maximum 50 megapixels

Step 2 / Output

Image Posterize controls

Choose 2 to 16 levels per RGB channel; fewer levels create stronger banding and more possible combined colours still remain. Pixel processing stays in this browser tab.

Create the posterized imageThe source file is not overwritten. Export creates a separate posterized image.
Keep this page open until the download begins.
01No server upload

The selected image is decoded and re-encoded inside this browser tab.

02Working copy released

After download, the preview URL, decoded bitmap, canvas, and selected source reference are cleared.

03Your download remains

Nirmion cannot remove the finished file from your device or browser download history.

Workflow guide

A controlled image posterize workflow

Each channel is quantized independently to the selected number of evenly spaced levels while spatial pixel dimensions remain unchanged. Review the result against the intended display rather than treating the setting as an objective correction.
A

What you need

Choose one authorised JPEG, PNG, or WebP image up to 20 MB and 12 million decoded pixels. Animated frames are not processed.

B

Social-ready choices

Test a limited-tone illustration treatment while inspecting gradients for intentional rather than accidental banding.

C

What you receive

Download a separate posterized image. Dimensions remain unchanged unless the selected encoder handles the source differently.

Decision guide

What image posterize changes

Each channel is quantized independently to the selected number of evenly spaced levels while spatial pixel dimensions remain unchanged.

Posterization is per-channel quantization, not palette optimization, dithering, vector tracing, or print colour separation. Browser-local processing avoids a Nirmion file upload, but it does not remove copies already stored elsewhere.

W3C Filter Effects Module Level 1

Useful image posterize checks

  1. Test a limited-tone illustration treatment while inspecting gradients for intentional rather than accidental banding.
  2. Create a reversible review copy while preserving the original image for comparison or later editing.
  3. Prepare a consistent derivative for an authorised design, publishing, or archival workflow.

Good to know

Important image boundaries

Why might a PNG not become smaller?
PNG is lossless and browsers do not expose a quality control for it. Choose WebP or JPEG when reducing file size matters more than exact lossless pixels.
Are animated images supported?
No. The workspace accepts still JPEG, PNG, and WebP files. Re-encoding an animated source would otherwise keep only one frame.
What does clearing the file mean?
Because processing is local, there is no Nirmion server copy to delete. The tab releases its working references after success; your downloaded output remains on your device.

Questions answered

Frequently asked questions

Does Image Posterize upload my image?

No. For supported JPEG, PNG, and WebP inputs, decoding, image posterize, canvas rendering, and export run in your current browser tab. Nirmion does not send the selected image to its API for this workflow. The downloaded file is a new derivative; your original device file remains unchanged and should be retained when future editing or verification matters.

What does Image Posterize change?

Each channel is quantized independently to the selected number of evenly spaced levels while spatial pixel dimensions remain unchanged. The operation is applied to decoded RGB pixels while the alpha channel is preserved. It does not resize the canvas, recover clipped source detail, identify subjects, or infer a professionally correct look. Inspect representative shadows, midtones, highlights, edges, text, and transparent areas before relying on the exported copy.

What are the limits of Image Posterize?

Posterization is per-channel quantization, not palette optimization, dithering, vector tracing, or print colour separation. The workspace accepts one supported still image up to 20 MB and limits pixel-intensive effects to 12 million decoded pixels for predictable browser memory use. Output also depends on the browser encoder and selected format. Animated images, raw camera development, colour-profile calibration, and batch processing are outside this tool's scope.