View the RGB and Luminance Histogram of an Image
Read the tonal distribution of any photo the way your camera does. Drop an image in and the tool plots a 256-level histogram for the red, green, blue, and luminance channels, so you can spot blown highlights, crushed shadows, and color casts at a glance. Toggle channels, read the per-channel min, max, and mean, and export the raw bins as CSV. Everything runs in your browser, so the photo never leaves your device.
How to read an image histogram
- Drop a photo in, or click to browse.
- Toggle the R, G, B, and Luma channels to inspect each one.
- Read the exposure from the shape: a pile at the right means highlights, a pile at the left means shadows.
- Use Copy CSV to export all 256 bins for spreadsheets or scripts.
Examples
Check a photo for clipping
A JPEG that looks slightly overexposed
A luminance histogram bunched against 255, confirming blown highlights
Frequently asked questions
Is my image uploaded anywhere?
No. The photo is decoded and analyzed entirely in your browser. It never leaves your device, so private images stay private.
How is the luminance channel calculated?
It uses the Rec. 709 weighting (0.2126 red + 0.7152 green + 0.0722 blue), the standard for perceived brightness. That matches the luminance view most cameras and editors show.
What does the histogram tell me about exposure?
The horizontal axis is brightness from black on the left to white on the right, and the height is how many pixels sit at each level. Pixels stacked hard against either edge mean clipped shadows or highlights with lost detail.
Can I export the data?
Yes. Copy CSV gives you 256 rows of value, red, green, blue, and luminance counts, ready to paste into a spreadsheet or feed to a script.
Does it use every pixel?
For speed the image is sampled down to about a 400 pixel long edge before counting. The shape of the histogram stays representative, which is what matters for judging exposure.
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