How to use the image histogram viewer
- Choose an image or drop it on the box. JPG, PNG, WebP, GIF, BMP and AVIF files up to 25 MB work; SVG does not.
- Tick the channels you want to see: red, green, blue and luminance. The legend shows each line style as well as its color.
- Switch to a log scale to see small counts next to large ones, and decide whether to ignore fully transparent pixels.
- Read the table for the mean, median, lowest, highest and the pixels clipped at 0 and 255, and use Download the counts as CSV to keep all 256 counts of each channel.
Reading a histogram
A histogram counts how many pixels have each value from 0 (darkest) to 255 (brightest). A picture that is dark overall has its counts piled to the left, a bright one to the right, and one with good contrast spreads across the whole range. Each color channel has its own histogram, and the luminance line shows the brightness the eye sees: 0.2126 red + 0.7152 green + 0.0722 blue, rounded to a whole value.
Clipping means pixels sitting at exactly 0 in shadows or 255 in highlights, where detail is lost. The table gives the number and the share of pixels at both ends for every channel. A tall spike at either end of the chart points to clipping, although a graphic with a pure white or black background will have one on purpose.
How the counting is done
Every pixel is counted exactly, in strips of rows, so a large photo does not need much memory. The bins add up to the number of pixels counted, and the page shows that total next to the size of the image as a check. Values are the ones your browser shows, after any embedded color profile and the photo's rotation are applied, and an animated GIF counts as its first frame.
Fully transparent pixels hold no visible color, so they are skipped by default; untick the box to count them as the stored color values. To pick a single color from an image use the Image Color Picker, to draw a histogram from numbers the Histogram Maker, and to change brightness the Adjust Image Brightness tool.
More file and image tools
To convert other files or edit an image, try the Reduce Image Colors Tool, PowerPoint Text Extractor and EPUB Text Extractor.
Assumptions and limits
- The image is a JPG, PNG, WebP, GIF, BMP or AVIF file that your browser can decode.
- Pixel values are read through the browser's canvas, so they follow its color handling.
- Luminance uses the Rec. 709 weights and is rounded half up to a whole value.
- The image is processed in your browser and is never uploaded.
Frequently asked questions
Why is my photo's luminance different from the average of its channels?
Luminance weights green most and blue least, as the eye does, so it is not the plain average of red, green and blue.
What does it mean when the log scale shows a flat floor?
On a log scale small counts are lifted, so values with few pixels become visible. A floor just above the baseline shows that every value has a few pixels.
Does a spike at 255 always mean a problem?
No. It means many pixels are at the top value. In a photo that can be blown highlights, but in a screenshot or logo with a white background it is expected.
Are the numbers the same as in my photo editor?
They are close, but an editor may use a different color space or weights for luminance. Counts for single channels should agree for the same file and color profile.