๐ Image Histogram Viewer
Drag and drop an image, or click to select
Upload an image to see a histogram of how many pixels fall at each brightness level (0-255) for the red, green, and blue channels, as well as overall luminance. Useful for checking a photo's exposure and color cast at a glance.
How to use
- Drag and drop an image, or click to select a file.
- The histogram for each channel and luminance is shown automatically.
How the calculation works
Shows how brightness is distributed in an image, as four graphs: red, green, blue and luminance. Reading the graph โข Horizontal axis: brightness (0 = black at the left, 255 = white at the right) โข Vertical axis: how many pixels have that brightness Luminance is 0.299 ร red + 0.587 ร green + 0.114 ร blue. Pixels that are more than half transparent are not counted.
Worked example
โข A snow scene: the mountain leans right (a bright image) โข A night scene: the mountain leans left (a dark image) โข A thin spike at the far right: blown-out highlights (areas clipped to pure white) โข Only the red mountain shifted right: an overall red cast
Things to be aware of
- Each of the four graphs is scaled so its own highest peak touches the top, so compare heights between colours only roughly.
- There is no single โgoodโ histogram shape. A snow scene leaning right is perfectly normal.
- Processing happens in your browser; the image is never uploaded.
FAQ
What does the histogram tell me?
The horizontal axis is brightness (0 = darkest, 255 = brightest), and the vertical axis is how many pixels have that brightness. A peak shifted left means a darker image, shifted right means a brighter one, and spikes at either extreme suggest clipped highlights or crushed shadows.
How is luminance (the gray line) calculated?
It's computed from each pixel's RGB values using weights that reflect human eye sensitivity (luminance = 0.299รR + 0.587รG + 0.114รB) โ the same standard luminance formula used in broadcast television (equivalent to ITU-R BT.601).
Is the image uploaded to a server?
No. All processing happens entirely in your browser โ the image is never sent to a server.