PPolySim OS

Histogram Equalization

Rescue a washed-out image by reshaping its intensity distribution. Watch the histogram and cumulative curve drive real contrast enhancement, live.

Histogram Equalization StudioLive

Controls

Method

Enhance a low-contrast image. Equalize spreads the intensity CDF across the full range; stretch is a linear min–max; gamma is a fixed tone curve.

Presets

▶ Run in Python

Data Inspector

Input presetLow contrast
MethodEqualize
Mean (before → after)124 → 129
Std (before → after)7.7 → 75.4
Range before107–147 (40)
Range after0–255 (255)

Governing equation

Reading this result: Equalization remaps intensities so the cumulative histogram becomes roughly linear, spreading the 40-level input across nearly the full 0–255 range (std 7.7 → 75.4). Contrast jumps because rarely-used levels are compressed and crowded levels are pulled apart — which also amplifies any noise in flat regions.

Runs locally in your browser — free forever. Scale to the cloud when reality gets heavy.

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How it works

Histogram equalization builds the intensity histogram of an image, forms its cumulative distribution function (CDF), and uses that CDF as a transfer function s = (L-1)·CDF(r) to spread crowded intensity levels across the full 0–255 range. Compare it against a linear min–max contrast stretch and a gamma tone curve on the same low-contrast, dark, washed-out, or bimodal test image — and see why equalization boosts local detail but can amplify noise in flat regions.

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Frequently asked questions

Is this histogram equalization contrast tool really free?
Yes. Histogram Equalization runs entirely in your browser using your device's own compute, so local use is free forever. You only pay Compute Tokens if you scale a job to the cloud.
Do I need to install anything?
No. Everything runs client-side in a modern browser — no downloads, no license, no account required to start.
Can I save or share my simulation?
Create a free account to save projects, and use a shareable embed or minted DOI to publish a live, interactive version anywhere.
How accurate are the results?
The solver uses established numerical methods, but results are for research and educational purposes and should be validated against experiment or professional review before you rely on them.