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Image Histogram — RGB & Luminance Tonal Analysis
Upload an image to view its RGB and luminance histograms with mean, median, and standard deviation. Spot blown highlights and crushed shadows, check exposure, and read the tonal range — free, in your browser, nothing uploaded.
View the RGB and luminance histograms of any image, complete with mean, median, and standard deviation for each channel. A histogram is the quickest way to judge exposure, spot blown highlights or crushed shadows, and read an image's overall tonal range. It is computed in your browser — nothing is uploaded.
How It Works
Choose a tool
Pick from 120+ tools to resize, convert, compress, or enhance your image.
Upload & edit
Drag and drop your image and adjust the settings. It stays on your device.
Download
Save your result instantly — no watermark, no sign-up required.
Why Image Machine?
Your files never leave your device
All processing runs locally in your browser. Your images are never uploaded to a server.
Completely free
Every tool is free, with no limits, no watermarks, and no hidden costs.
Lightning fast
No upload waiting — your images are processed instantly on your own device.
Professional quality
Pixel-perfect output with full control over format, size, and quality.
Frequently Asked Questions
What does an image histogram show?
A histogram plots how many pixels fall at each brightness level, from black on the left to white on the right. The shape tells you whether an image is dark, bright, low-contrast, or well-balanced across its tones.
How do I tell if my photo is over- or under-exposed?
Look at the ends of the histogram. A tall spike piled against the right edge means blown-out highlights (overexposure); a spike against the left edge means crushed shadows (underexposure). A healthy image spreads across the range without clipping.
What do the mean, median, and standard deviation mean?
The mean is the average brightness, the median is the middle value, and the standard deviation measures contrast — how widely the tones are spread. A low standard deviation indicates a flat, low-contrast image.
Is my image uploaded to build the histogram?
No. The histogram and statistics are computed in your browser, so the image never leaves your device.