Online Image Histogram Tool

What this tool actually does

Analyzes one image and generates an RGB channel histogram graphic rather than modifying the source. There are no adjustable controls, numeric-bin table, luminance mode, logarithmic scale, clipping alert or CSV export.

Checkable behavior

The browser counts exact 8-bit red, green and blue values in three separate 256-bin arrays. Pixels with alpha 0 are ignored; any nonzero-alpha pixel counts once without opacity weighting. Peaks show channel frequency, not the positions of those pixels in the image.

Controls, output and limitations

The result is a fixed 760 by 380 white PNG canvas. Red, green and blue lines are drawn at 72 percent opacity on the same axes and scaled to the largest channel-bin count. Horizontal endpoints are labelled 0 and 255; overlapping translucent lines can visually mix.

Verified sample: visible RGB(10,20,30) and RGB(10,40,50) give red bin 10 count 2 and green bins 20 and 40 count 1 each. A fully transparent RGB(200,210,220) pixel contributes nothing. A fully transparent image uses a safe empty baseline rather than invalid coordinates.

Input is one browser-decodable image up to 25 MiB and 24,000,000 pixels. Generate performs local analysis; download saves a PNG graph named from the source base plus -histogram.png. It does not export raw counts, diagnose exposure automatically, extract a palette or preserve source metadata.