ppmhist

   Updated: 22 October 2003
   Table Of Contents

NAME

   ppmhist - print a histogram of the colors in a PPM image

SYNOPSIS

   ppmhist   [-hexcolor	 |  -float  | -colorname | -map] [-nomap]
[-noheader]
   [-sort={frequency,rgb}] [ppmfile]

DESCRIPTION

   This program is part of Netpbm.

   ppmhistreads a PPM image as input and generates a histogram of
the colors in
   the	image,	i.e. a list of all the colors and how many pixels
of each color
   are in the image.

  Output Format

   The output is one line for each color in the input image.

   By  default,	 there are two lines of column header at the top.
Use the
   -noheader option to suppress those lines.

   In	each  line,  ppmhist  identifies the color by red, green,
and blue
   components. By default, it lists each of these in decimal, us-
ing the exact
   values that are in the PPM input. So if the image has a maxval
of 255, the
   numbers in the listing range from 0 to 255. With the -hexcolor
option, you
   can	change	these numbers to hexadecimal. With the -float op-
tion, the numbers
   are fractional, adjusted to a maxval of 1.

   Each line lists the luminosity of the color. It is in  decimal
on the same
   scale as the rgb values (see above).

   Each	 line  lists  the number of pixels in the image that have
the color. This
   is in decimal.

OPTIONS

   -sort={frequency,rgb}
	  The -sort option determines the order in which the col-
ors are listed
	  in the output. frequency means to list them in order of
how pixels in
	  the input image have the color, with	the  most  repre-
sented colors
	  first. rgb means to sort them first by the intensity of
the red
	  component of the color, the of the green, then  of  the
blue, with the
	  least intense first.
	  The default is frequency.
   -hexcolor
	  Print	 the  color components in hexadecimal. See output
format.
	  You may not specify this option along	 with  -float  or
map.
   -float
	  Print the color components and the luminosity as float-
ing point
	  numbers in the range [0,1]. See output format.
	  You may not specify this option along with -hexcolor or
map.
	  This	option was added in Netpbm 10.19 (November 2003).
   -map
	  Generates a PPM file of the  colormap	 for  the  image,
with the color
	  histogram as comments. See output format.
	  You  may  not	 specify this option along with -float or
hexcolor.
   -nomap
	  Generates the histogram for human reading. This is  the
default.
   -colorname
	  Add the color name to the output. This is the name from
the system
	  color dictionary. If the exact color is not in the col-
or dictionary,
	  it  is  the closest color that is in the dictionary and
is preceded by
	  a '*'. If you don't have a system color dictionary, the
program
	  fails.
	  This option was added in Netpbm 10.10 (October 2002).
   -noheader
	  Do not print the column headings.



SEE ALSO

   ppm, pgmhist, pnmcolormmap, pnmhistmap, ppmchange


AUTHOR

   Copyright (C) 1989 by Jef Poskanzer.
     _________________________________________________________________



Table Of Contents

     * NAME
     * SYNOPSIS
     * DESCRIPTION
     * OPTIONS
     * SEE ALSO
     * AUTHOR

UNIX/Linux commands referenced on this page:

1. as
2. column
3. at
4. red
5. which
6. sort
7. file
8. pgmhist
9. pnmhistmap