This program is part of Netpbm.
pgmhist reads a PGM image as input and prints a histogram of the gray values or other gray value distribution metrics.
If you specify none of -median, -quartile, or -decile, pgmhist prints a complete histogram showing how many pixels of each possible gray value exist in the image. Along with each gray value, it tells you how many pixels are more black and more white that it.
-median, -quartile, and -decile options cause pgmhist instead to print the indicated quantiles. Each quantile is a gray value that actually appears in the image (as opposed to fractional values that are sometimes used for quantiles). The 3rd quartile is the least gray value for which at least 75% of the pixels are as dark or darker than it. The 4th quartile is the brightest gray value that appears in the image.
This option causes pgmhist to print the median gray value.
You may specify at most one of -median, -quartile, and -decile.
This option was new in Neptbm 10.61 (December 2012).
This option causes pgmhist to print the four quartile gray value.
You may specify at most one of -median, -quartile, and -decile.
This option was new in Neptbm 10.61 (December 2012).
This option causes pgmhist to print the ten decile gray value.
You may specify at most one of -median, -quartile, and -decile.
This option was new in Neptbm 10.61 (December 2012).
This option causes pgmhist to print the information in a way easily digestible by a machine as opposed to a human.
For the quantiles, there is one line per quantile, in quantile order, and it consists of the gray value of the quantile in decimal with no leading zeroes.
For the full histogram output, it consists of one line per possible gray value (whether that value appears in the image or not), in order of the gray values. The line consists of two tokens separated by a space. The first is the gray value; the second is the number of pixels in the image that have that gray value. Both are decimal numbers without leading zeroes.
This option was new in Neptbm 10.61 (December 2012).