ppmhist



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




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(1).

       ppmhistreads a PPM image as input and generates a histogram of the col-
       ors  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 read-
       able 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 com-
       ponents.   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 -hex-
       color 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 decimal.


       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 palette.  The image is a single row with  one  column  for
       each distinct color in the image.




OPTIONS

       -sort={frequency,rgb}
              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 rep-
              resented 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.


       -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 floating 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
              color dictionary, it is the closest color that is in the dictio-
              nary 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(1), pgmhist(1), pnmcolormmap(1), pnmhistmap(1), ppmchange(1)



AUTHOR

       Copyright (C) 1989 by Jef Poskanzer.



netpbm documentation             24 June 2005           Ppmhist User Manual(0)

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