ABSTRACT
The histogram is a stock control chart for that warehouse. It lists the number of pixels in the image at each of 256 levels. Sometimes the separate red, green and blue channels are shown as three charts, each with 256 levels. A dark scene will show a left-biased histogram; an average scene will look like a hill centred on the middle of the chart; a light scene will be biased towards the right. A high-contrast scene has lots of dark tones and lots of light tones but very few grey or intermediate tones. The histogram for this kind of image will be a strong U-shaped distribution, with peaks at the left and right of the chart, and very little in the middle.
