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Ppmhist User Manual(0)							   Ppmhist User Manual(0)

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

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

       This program is part of Netpbm(1)

       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 in one of two basic formats:  a report for humans and a PPM image for use by
       programs.  The PPM image is actually quite readable by humans too.

       Human Report

       You get this format by specifying (or defaulting to) the -nomap option.

       The format 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, using 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 option, 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  deci-

       PPM Output

       You get this format with the -map option.

       The  output  file is a genuine PPM image, but it is PPM Plain format and contains comments
       so that it is not a lot different from the human report described above.

       As a PPM image, it can be useful as input to other programs that need some  kind  of  pal-
       ette.  The image is a single row with one column for each distinct color in the image.

	      The -sort option determines the order in which the colors 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 represented colors first.  rgb means to sort them first by the
	      intensity of the red component of the color, then of the green, then of  the  blue,
	      with the least intense first.

	      The default is frequency.

	      Print the color components in hexadecimal.  See output format <#output> .

	      You may not specify this option along with -float or map.

       -float Print  the  color  components  and  the luminosity as floating point numbers in the
	      range [0,1].  See output format <#output> .

	      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 <#output> .

	      You may not specify this option along with -float or hexcolor.

       -nomap Generates the histogram for human reading.  This is the default.

	      Add  the	color  name  to  the  output.	This  is  the  name from the system color
	      dictionary <libppm.html#rgb.txt> .  If the exact color is not in the color  dictio-
	      nary,  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).

	      Do not print the column headings.

       ppm(1) , pgmhist(1) , pnmcolormmap(1) , pnmhistmap(1) , ppmchange(1)

       Copyright (C) 1989 by Jef Poskanzer.

netpbm documentation			   24 June 2005 		   Ppmhist User Manual(0)
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