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pgmtoppm
!!!pgmtoppm
NAME
SYNOPSIS
DESCRIPTION
NOTE - MAXVAL
SEE ALSO
AUTHOR
----
!!NAME


pgmtoppm - colorize a PGM (grayscale) image into a PGM (color) image
!!SYNOPSIS


__pgmtoppm__ ''colorspec'' [[''pgmfile'']__
pgmtoppm__ ''colorspec1''__-__''colorspec2''
[[''pgmfile'']__
pgmtoppm -map__ ''mapfile''
[[''pgmfile'']
!!DESCRIPTION


Reads a PGM as input. 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 intensities of the specified
color.


If you specify two color arguments (separated by a dash),
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.


You can specify the color in one of five ways:


o


A name, from an X11-style color names file.


o


An X11-style hexadecimal specifier: rgb:r/g/b, where r g and
b are each 1- to 4-digit hexadecimal numbers.


o


An X11-style decimal specifier: rgbi:r/g/b, where r g and b
are floating point numbers between 0 and 1.


o


For backwards compatibility, an old-X11-style hexadecimal
number: #rgb, #rrggbb, #rrrgggbbb, or
#rrrrggggbbbb.


o


For backwards compatibility, a triplet of numbers separated
by commas: r,g,b, where r g and b are floating point numbers
between 0 and 1. (This style was added before MIT came up
with the similar rgbi style.)


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.
!!NOTE - MAXVAL


The
pgmtoppm__, like all Netpbm programs, can
accept a PBM file as if it were PGM. The maxval of this
image is 1, because only two gray values are needed: black
and white. 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 either 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 __pnmdepth__ on
the way into __pgmtoppm__ to increase its depth to
something that would give you the resolution you need to get
your desired color. In this case, __pnmdepth 16__ would
do it. Or spare yourself the unnecessary thinking and just
say __pnmdepth 255 .__
!!SEE ALSO


pnmdepth(1), rgb3toppm(1), ppmtopgm(1),
ppmtorgb3(1), ppm(5),
__pgm(5)__
!!AUTHOR


Copyright (C) 1991 by Jef Poskanzer.
----

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Last edited on Tuesday, June 4, 2002 12:22:41 am by "perry"

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