Online Image Histogram Equalization Tool

What Online Image Histogram Equalization Tool actually does

Applies whole-image luminance histogram equalization to one image with no adjustable processing controls. Loading shows the source only; press Generate to calculate and preview the equalized PNG.

Checkable example

Alpha and source dimensions are retained. A constant-luminance image is left unchanged. Verified two-pixel grayscale input 50 and 150 maps to 0 and 255 while preserving alpha; a single RGB(100,150,200) pixel stays unchanged because there is only one occupied luminance level.

Controls, output and limits

The browser builds a 256-bin histogram from rounded weighted luminance Y=0.299R+0.587G+0.114B. Its cumulative distribution maps the first occupied luminance to 0 and the last to 255. The mapped-minus-original luminance delta is added equally to R,G,B, then channels clamp to 0..255.

This method can increase separation in a low-contrast scan, but adding the same luminance delta preserves channel differences only until a channel clips. It is not local adaptive equalization, CLAHE, automatic exposure scoring, denoising or recovery of detail already clipped in the source.

Input is one browser-decodable image up to 25 MiB (26 214 400 B) and 24,000,000 pixels. Generate after loading, compare the preview with the source and download PNG named from the source base plus -equalize.png. Processing stays in the browser and source metadata is not preserved in the canvas export.