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
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.)
If a pixel matches two different
oldcolors,
ppmchange
replaces it with the
newcolor
of the leftmost specified one.
OPTIONS
-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 chrominance, 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 analysis.
-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.