Free web tool
Analyze RGB and luminance histograms plus basic pixel statistics in the browser.
Plot the distribution of R, G, B, and luminance values from 0 to 255. It helps you see whether an image is concentrated in shadows or highlights and whether one color channel dominates, instead of relying on appearance alone.
The horizontal axis runs from 0 to 255 and the height shows how many sampled pixels land at each value. The tool overlays R, G, B, and luminance, where luminance uses perceptual weighting rather than a simple RGB average.
A distribution pushed left contains more dark values; one pushed right contains more bright values.
Previously, a 4 px step advanced through the flattened pixel array rather than sampling a true 4 px grid. v1.49 fixes this: 4 px now means every fourth pixel in x and every fourth row in y.
Use 1 px when you want every pixel; larger steps make analysis much faster on large images.
Fully transparent pixels can still store RGB values even though those colors are invisible. Including them can make averages and histograms disagree with what the image looks like.
v1.49 defaults to excluding fully transparent pixels. Turn that option off only when you intentionally want to inspect the hidden RGB data.
Two images can have the same average luminance but very different distributions: one clustered in midtones, another split between deep shadows and bright highlights.
Treat averages as a quick summary and read the histogram shape too. To edit the image afterward, use Brightness / contrast / saturation.