Read an image's histogram
The exposure truth-teller: are the shadows crushed, the highlights gone, the channels balanced?
Tools used in this guide
The job
A photo can look fine on a dim screen and still have no real blacks — the histogram shows what the pixels actually contain: 256 bins per RGB channel plus luminance.
Load and read
Drop any image ≤ 25 MiB. The chart draws the three channels and luminance; stats report the share of pixels clipped to pure black or pure white.
Worked example
A snow scene with the luminance piled at 230–255 and 8 % pure white is overexposed even if it 'looks okay'; a histogram hugging 0–40 is night, not a display problem.
Where it stops
It reports, never alters — download the chart as PNG, not a corrected image. Alpha is ignored; the histogram is of the visible RGB.