ppmchange(1)                General Commands Manual               ppmchange(1)

       ppmchange  -  change  all  pixels of one color to another in a portable

       ppmchange [ -closeness closeness_percent ] [ -remainder remainder_color
       ] [ oldcolor newcolor ] ...  [ppmfile]

       Reads  a  portable  pixmap as input.  Changes all pixels of oldcolor to
       newcolor.  You may specify up to 256  oldcolor/newcolor  pairs  on  the
       command  line.   ppmchange  leaves  all colors not mentioned unchanged,
       unless you specify the -remainder option, in which case  they  are  all
       changed to the single specified color.

       You can specify that colors similar, but not identical, to the ones you
       specify get replaced by specifying a "closeness" factor.

       The colors can be specified in five ways:

       o      A name, assuming that a pointer to an X11-style color names file
              was compiled in.

       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 num-
              ber: #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.)

              If  a  pixel matches two different oldcolors, ppmchange replaces
              it with the newcolor of the leftmost specified one.

       -closeness closeness_percent
              closeness is an integer per centage indicating how close to  the
              color  you  specified  a  pixel  must  be  to  get replaced.  By
              default, it is 0, which means the pixel must be the exact  color
              you specified.

              A  pixel  gets  replaced if the distance in color between it and
              the color you specified is less than or equal to closeness.

              The "distance" in color is defined as the cartesian sum  of  the
              individual  differences  in  red,  green,  and  blue intensities
              between the  two  pixels,  normalized  so  that  the  difference
              between black and white is 100%.

              This  is probably simpler than what you want most the time.  You
              probably would like to change colors that have  similar  chromi-
              nance,  regardless of their intensity.  So if there's a red barn
              that is variously shadowed, you want the  entire  barn  changed.
              But  because  the  shadowing  significantly  changes  the  color
              according to ppmchange's distance formula, parts of the barn are
              probably  about as distant in color from other parts of the barn
              as they are from green grass next to the barn.

              Maybe ppmchange will be enhanced  some  day  to  do  chrominance

       -remainder color
              ppmchange  changes all pixels which are not of a color for which
              you specify an explicit replacement color on the command line to
              color color.

              An example application of this is

              ppmchange -remainder=black red red

              to lift only the red portions from an image, or

              ppmchange -remainder=black red white | ppmtopgm

              to create a mask file for the red portions of the image.

       pgmtoppm(1), ppmcolormask(1), ppm(5)

       Wilson  H.  Bent. Jr. (whb@usc.edu) with modifications by Alberto Acco-
       mazzi (alberto@cfa.harvard.edu)

                                07 January 2001                   ppmchange(1)
Man Pages Copyright Respective Owners. Site Copyright (C) 1994 - 2022 Hurricane Electric. All Rights Reserved.