Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages


home | help
Pgmtoppm User Manual(0)				       Pgmtoppm	User Manual(0)

       pgmtoppm	- colorize a PGM (grayscale) image into	a PPM (color) image

       pgmtoppm	 colorspec  [pgmfile] pgmtoppm colorspec1-colorspec2 [pgmfile]
       pgmtoppm	-map=mapfile [pgmfile]

       Minimum unique abbreviation of option is	acceptable.  You may use  dou-
       ble  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.

       This program is part of Netpbm(1).

       pgmtoppm	 reads a PGM as	input and produces a PPM file as output	with a
       specific	color assigned to each gray value in the input.

       If you specify one color	argument, black	in the pgm  file  stays	 black
       and  white  in  the  pgm	file turns into	the specified color in the ppm
       file.  Gray values in between are linearly mapped to differing intensi-
       ties of the specified color.

       If  you specify two color arguments (separated by a hyphen), then black
       gets mapped to the first	color and white	gets mapped to the second  and
       gray  values in between get mapped linearly (across a three dimensional
       space) to colors	in between.

       Specify the  color  (color)  as	described  for	the  argument  of  the
       pnm_parsecolor()	library	routine	<libnetpbm_image.html#colorname> .

       Also,  you  can	specify	 an entire colormap with the -map option.  The
       mapfile is just a ppm file; it can be any shape,	all  that  matters  is
       the colors in it	and their order.  In this case,	black gets mapped into
       the first color in the map file,	and white gets mapped to the last  and
       gray  values in between are mapped linearly onto	the sequence of	colors
       in between.  The	maxval of the output image is the maxval  of  the  map

       A more direct way to specify a particular color to replace each partic-
       ular gray level is to use pamlookup.  You make an index file  that  ex-
       plicitly	associates a color with	each possible gray level.

       When you	don't use -map,	the "maxval," or depth,	of the output image is
       the same	as that	of the input image.  The maxval	affects	the color res-
       olution,	 which	may  cause quantization	errors you don't anticipate in
       your output.  For example, you have a simple black and white image as a
       PGM  with maxval	1.  Run	this image through pgmtoppm 0f/00/00 to	try to
       make the	image black and	faint red.  Because the	output image will also
       have  maxval  1,	there is no such thing as faint	red.  It has to	be ei-
       ther full-on red	or black.  pgmtoppm rounds the color 0f/00/00 down  to
       black, and you get an output image that is nothing but black.

       The  fix	 is easy: Pass the input through pamdepth on the way into pgm-
       toppm to	increase its depth to something	that would give	you the	 reso-
       lution  you  need to get	your desired color.  In	this case, pamdepth 16
       would do	it.  Or	spare yourself the unnecessary thinking	and  just  say
       pamdepth	255.

       PBM  input  is  a  special  case.   While you might think this would be
       equivalent to a PGM with	maxval 1 since only two	gray levels are	neces-
       sary  to	 represent a PBM image,	pgmtoppm, like all Netpbm programs, in
       fact treats it as a maxval of 255.

       pamdepth(1), rgb3toppm(1), ppmtopgm(1), ppmtorgb3(1), ppm(5), pgm(5)

       Copyright (C) 1991 by Jef Poskanzer.

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

netpbm documentation	       10 December 2006	       Pgmtoppm	User Manual(0)


Want to link to this manual page? Use this URL:

home | help