Image Histogram
FreeView the Red, Green, Blue, or Luminosity histogram of a photo, with an overlay mode and Min/Max/Mean/Median/StdDev stats, directly in your browser.
Runs entirely in your browser. Your image is never uploaded anywhere.
Click to choose an image, or drag and drop one here
Recent Activity
Visible to everyone. Last 20 uses across all visitors, newest first.
800×1000 · Luminosity · mean 97.0, std.dev 74.4
1 month ago
What this tool does
Draws a 256-bin histogram of your photo's Red, Green, Blue, or Luminosity channel directly in your browser, or overlays all three color channels at once to check for color balance. Below the chart, see Min, Max, Mean, Median, and Standard Deviation for the selected channel, and toggle a logarithmic scale to reveal detail hidden behind a dominant spike.
How It Works
For every pixel, the tool reads the chosen channel's value (0-255) and increments a counter for that exact value; Luminosity instead combines all three channels first, using the standard 0.299 red + 0.587 green + 0.114 blue weighting, before counting. The resulting 256 counts are drawn as bars scaled to the tallest bar in the set, or, with Logarithmic scale enabled, scaled by the logarithm of each count instead of the raw count, which shrinks the gap between a huge spike and everything else. The statistics below the chart are all derived from the same 256 counts: Min and Max are the lowest and highest values that appear at all, Mean is the count-weighted average value, Median is the value at which half of all pixels fall below and half fall at or above, and Standard Deviation measures how spread out the values are around the mean, a tight cluster of similar tones giving a low number and a wide spread of tones giving a high one.
Problems it solves
- Checking whether a photo is underexposed, overexposed, or has good tonal range before editing it further.
- Spotting an unwanted color cast by seeing whether one channel's histogram is shifted away from the others.
- Comparing the exact brightness or contrast of two photos numerically instead of just by eye.
Frequently asked questions
›What does a histogram actually show me?
It counts how many pixels in your photo have each possible value, from 0 to 255, for whichever channel you pick, and draws that as 256 bars side by side. A tall bar on the left means many pixels are dark in that channel; a tall bar on the right means many pixels are bright.
›What is the difference between the Red, Green, Blue, and Luminosity channels?
Red, Green, and Blue show the distribution of just that one color channel's raw value at every pixel. Luminosity instead combines all three into a single "how bright does this pixel look to the human eye" value (weighted more toward green, since human vision is most sensitive to it), which is closer to what a black-and-white conversion or a camera's exposure meter would show.
›Why does the "All (overlay)" view look so different from a single channel?
It draws the Red, Green, and Blue histograms on top of each other in their own color, semi-transparent, so you can see at a glance whether the color channels are balanced (their peaks roughly overlap) or skewed (one channel's bars are shifted noticeably left or right of the others, which usually signals a color cast).
›When should I turn on Logarithmic scale?
Most real photos have one or two very tall spikes (often at pure black or pure white) that make every other, smaller bar look flat at the default linear scale. Logarithmic scale compresses that tall spike down and stretches the smaller bars up, so you can actually see detail throughout the whole tonal range instead of just the dominant spike.
›Is my photo uploaded anywhere?
No. The histogram is calculated locally in your browser using the HTML canvas API. Nothing is sent to a server.
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