Manual: pnmhistmap

Pnmhistmap User Manual(1)			   General Commands Manual			   Pnmhistmap User Manual(1)

NAME
       pnmhistmap - draw a histogram for a PGM or PPM file

SYNOPSIS
       pnmhistmap

       [-red] [-green] [-blue]

       [-black] [-white]

       [-max N]

       [-lval] [-rval]

       [-height] [-width]

       [-dots]

       [-verbose]

       [pnmfile]

       Minimum	unique	abbreviation of option is acceptable.  You may use double hyphens instead of single hyphen to denote
       options.	 You may use white space in place of the equals sign to separate an option name from its value.

DESCRIPTION
       This program is part of Netpbm(1).

       pnmhistmap reads a PNM image as input and produces an image showing a histogram of the color (or gray) values in	 the
       input.	A  PGM input results in a PBM output.  A PPM input results in a PPM output with three overlaid histograms: a
       red one for the red input, a green one for the green input, and a blue one for the blue input.

       For example, from the following image produces the following histogram:

       image histogram from image

       If the input is PBM, pnmhistmap produces an error message and no output image.

OPTIONS
       In addition to the options common to all programs based on libnetpbm (most notably -quiet, see  Common Options ), pn‐
       mhistmap recognizes the following command line options:

       -red

       -green

       -blue  Include the indicated color component in the output.  If you specify none of  these,  pnmhistmap	include	 all
	      three.

	      These options are meaningless if the input is PGM.

	      These  options  were  new	 in  Netpbm 10.26 (January 2005).  Before that, pnmhistmap always included all three
	      color components.

       -dots  Plot the histogram as dots.  By default, pnmhistmap plots bars.

	      Example of dots:.B -dots example

	      This option was new in Netpbm 10.26 (January 2005).  Before that, pnmhistmap always plotted bars.

       -lval minpixval

       -rval maxpixval
	      These options specify the range of intensity values to include.  pnmhistmap ignores intensities less than min‐
	      pixval and greater than maxpixval.  So the left side of the histogram corresponds to minpixval and  the  right
	      side corresponds to maxpixval.

	      By default, pnmhistmap plots the entire possible range: zero to the maxval.

	      These  options  were  new in Netpbm 10.26 (January 2005).	 Before that, pnmhistmap always plotted from zero to
	      the maxval.

       -height

       -width These options specify the dimensions, in pixels of the histogram image.

	      The default height is 200 pixels.

	      The default width is one pixel for each plotted intensity value (so it's controlled by the maxval of the image
	      and the -lval and -rval options).	 The "count buckets" in the histogram are always one  pixel  wide.   If	 you
	      specify  a width less than the number of plotted intensity values, a bucket represents more than one intensity
	      value.  If you specify a width greater that the number of plotted intensity values, some buckets represent  no
	      color (the count is zero).

	      This  option was new in Netpbm 10.26 (January 2005).  Before that, the dimensions were always what the default
	      is today.

       -black Ignore the count of black pixels when scaling the histogram.

       -white Ignore the count of white pixels when scaling the histogram.

	      The -black and -white options, which can be used separately or together, are useful for images  with  a  large
	      percentage  of  pixels  whose value is zero or 255, which can cause the remaining histogram data to become un‐
	      readably small.  Note that, for color inputs, these options apply to all colors; if, for	example,  the  input
	      has a large number of bright-red areas, you will probably want to use the -white option.

       -max N Force  the  scaling  of  the  histogram to use N as the largest-count value.  This is useful for inputs with a
	      large percentage of single-color pixels which are not black or white.

       -verbose
	      Report the progress of making the histogram, including the largest-count value used to scale the output.

LIMITATIONS
       pnmhistmap assumes maxval is always 255.	 Images with a smaller maxval will only use the lower-value side of the his‐
       togram.	You can overcome this either by piping the input through pamdepth or by cutting and scaling the	 lower-value
       side of the histogram.  Neither is a particularly elegant solution to the problem.

SEE ALSO
       pgmhist(1), ppmhist(1), pgm(1), ppm(1)

AUTHOR
       Wilson H. Bent. Jr. (whb@usc.edu).

DOCUMENT SOURCE
       This manual page was generated by the Netpbm tool 'makeman' from HTML source.  The master documentation is at

	      http://netpbm.sourceforge.net/doc/pnmhistmap.html

netpbm documentation					13 July 2009				   Pnmhistmap User Manual(1)