pixstat — list statistics related to a color pix image
pixstat will take the given pix(5) format file, or read from standard in. A collection of statistics related to the pixel intensities is produced for each color plane (red, green, and blue). These include: the number of pixels (and the square root of this which is the file dimensions if square); the max and min values; the mean; the median (dividing line where half the pixels are above this value, half below); the mode (most frequently occurring value) and the number of pixels at this value; the variance, standard deviation, and skew.
The
-v
flag will also dump a histogram of the pixel values.
Since the pixel values are quantized (each color having discrete values from 0 to 255), the statistics can be computed from "lump sums" after building a histogram of the input. This results in a fantastic savings in computation while also making a single pass over the input file sufficient.