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<P><CENTER>
<a href="0407-0407.html">Previous</A> | <a href="../ewtoc.html">Table of Contents</A> | <a href="0412-0414.html">Next</A></CENTER></P>
<A NAME="PAGENUM-408"><P>Page 408</P></A>
<H3><A NAME="ch01_ 300">
ppmhist
</A></H3>
<P>ppmhist—Print a histogram of a portable pixmap
</P>
<P><B>
SYNOPSIS
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
ppmhist [ppmfile]
</PRE>
<!-- END CODE SNIP //-->
<P><B>
DESCRIPTION
</B>
</P>
<P>ppmhist reads a portable pixmap as input and generates a histogram of the colors in the pixmap.
</P>
<P><B>
SEE ALSO
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
ppm(5), pgmhist(1)
</PRE>
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<P><B>
AUTHOR
</B>
</P>
<P>Copyright" 1989 by Jef Poskanzer.
</P>
<P>3 April 1989
</P>
<H3><A NAME="ch01_ 301">
ppmmake
</A></H3>
<P>ppmmake—Create a pixmap of a specified size and color
</P>
<P><B>
SYNOPSIS
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
ppmmake color width height
</PRE>
<!-- END CODE SNIP //-->
<P><B>
DESCRIPTION
</B>
</P>
<P>ppmmake produces a portable pixmap of the specified color, width, and height.
</P>
<P>The color can be specified in five ways:
</P>
<UL>
<LI> A name, assuming that a pointer to an X11-style color names file was compiled in.
<LI> An X11-style hexadecimal specifier:
rgb:r/g/b, where r, g, and b are each 1- to 4-digit hexadecimal numbers.
<LI> An X11-style decimal specifier:
rgbi:r/g/b, where r, g, and b are floating-point numbers between 0 and 1.
<LI> For backwards compatibility, an old-X11-style hexadecimal number:
#rgb, #rrggbb, #rrrgggbbb, or #rrrrggggbbbb.
<LI> 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.)
</UL>
<P><B>
SEE ALSO
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
ppm(5), pbmmake(1)
</PRE>
<!-- END CODE SNIP //-->
<P><B>
AUTHOR
</B>
</P>
<P>Copyright" 1991 by Jef Poskanzer.
</P>
<P>24 September 1991
</P>
<H3><A NAME="ch01_ 302">
ppmmix
</A></H3>
<P>ppmmix—Blend together two portable pixmaps
</P>
<P><B>
SYNOPSIS
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
ppmmix fadefactor ppmfile1 ppmfile2
</PRE>
<!-- END CODE SNIP //-->
<A NAME="PAGENUM-409"><P>Page 409</P></A>
<P><B>
DESCRIPTION
</B></P>
<P>ppmmix reads two portable pixmaps as input and mixes them together using the specified fade factor. The fade factor may
be in the range from 0.0 (only ppmfile1's image data) to 1.0 (only
ppmfile2's image data). Anything in between gains a
smooth blend between the two images.
</P>
<P>The two pixmaps must have the same size.
</P>
<P><B>
SEE ALSO
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
ppm(5)
</PRE>
<!-- END CODE SNIP //-->
<P><B>
AUTHOR
</B>
</P>
<P>Copyright" 1993 by Frank Neumann.
</P>
<P>16 November 1993
</P>
<H3><A NAME="ch01_ 303">
ppmnorm
</A></H3>
<P>ppmnorm—Normalize the contrast in a portable pixmap
</P>
<P><B>
SYNOPSIS
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
ppmnorm[-bpercent N | -bvalue N][-wpercent N | -wvalue N][ppmfile]
</PRE>
<!-- END CODE SNIP //-->
<P><B>
DESCRIPTION
</B>
</P>
<P>ppmnorm reads a portable pixmap as input; normalizes the contrast by forcing the lightest pixels to white, the darkest pixels
to black, and linearly rescaling the ones in between; and produces a portable pixmap as output.
</P>
<P>It works by computing the relative gray level of each pixel as
with ppmtopgm, and uses those values to scale the RGB
levels. Note that this is different from using
pgmnorm on the individual red, green, and blue graymaps (as produced by
ppmtorgb3) and recombining them.
</P>
<P><B>
OPTIONS
</B>
</P>
<P>By default, the darkest two percent of all pixels are mapped to black, and the lightest one percent are mapped to white.
You can override these percentages by using the
-bpercent and -wpercent flags, or you can specify the exact pixel values to
be mapped by using the -bvalue and -wvalue flags. Appropriate numbers for the flags can be gotten from the
ppmhist tool. If you just want to enhance the contrast, then choose values at elbows in the histogram; for example, if value 29 represents
3 percent of the image but value 30 represents 20 percent, choose
30 for bvalue. If you want to lighten the image, then
set bvalue to 0 and just fiddle with wvalue; similarly, to darken the image, set
wvalue to maxval and play with bvalue.
</P>
<P>All flags can be abbreviated to their shortest unique prefix.
</P>
<P><B>
SEE ALSO
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
pgmnorm(1), ppmhist(1), ppm(5)
</PRE>
<!-- END CODE SNIP //-->
<P><B>
AUTHOR
</B>
</P>
<P>Wilson H. Bent, Jr. (whb@usc.edu), heavily based on the
pgmnorm filter by Jef Poskanzer.
</P>
<P>7 October 1993
</P>
<H3><A NAME="ch01_ 304">
ppmntsc
</A></H3>
<P>ppmntsc—Make a portable pixmap look like it is taken from an American
TV show
</P>
<P><B>
SYNOPSIS
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
ppmntsc dimfactor [ppmfile]
</PRE>
<!-- END CODE SNIP //-->
<A NAME="PAGENUM-410"><P>Page 410</P></A>
<P><B>
DESCRIPTION
</B>
</P>
<P>ppmntsc reads a portable pixmap as input and dims every other row of image data down by the specified dim factor.
This factor may be in the range of 0.0 (the alternate lines are totally black) to 1.0 (original image).
</P>
<P>This creates an effect similar to what I saw once in the video clip "You Could be Mine" by Guns'n' Roses. In the scene
I'm talking about you can see John Connor on his motorbike, looking up from the water trench (?) he's standing in. While
the camera pulls back, the image becomes "normal" by brightening up the alternate rows of it. I thought this would be
an interesting effect to try in MPEG. I did not yet check this out, however. Try for yourself.
</P>
<P><B>
SEE ALSO
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
ppm(5), ppmdim(1)
</PRE>
<!-- END CODE SNIP //-->
<P><B>
AUTHOR
</B>
</P>
<P>Copyright" 1993 by Frank Neumann.
</P>
<P>16 November 1993
</P>
<H3><A NAME="ch01_ 305">
ppmpat
</A></H3>
<P>ppmpat—Make a pretty pixmap
</P>
<P><B>
SYNOPSIS
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
ppmpat -gingham2|-g2|-gingham3| -g3|-madras|-tartan| -poles|-squig|-camo|
-anticamo width height
</PRE>
<!-- END CODE SNIP //-->
<P><B>
DESCRIPTION
</B>
</P>
<P>ppmpat produces a portable pixmap of the specified width and height, with a pattern in it.
</P>
<P>This program is mainly to demonstrate use of the
ppmdraw routines, a simple but powerful drawing library. See the
ppmdraw.h include file for more information on using these routines. Still, some of the patterns can be rather pretty. If you have a
color workstation, something like ppmpat -squig 300 300 | "ppmquant
128" should generate a nice background.
</P>
<P><B>
OPTIONS
</B>
</P>
<P>The different flags specify various different pattern types:
</P>
<TABLE>
<TR><TD>
-gingham2
</TD><TD>
A gingham check pattern. Can be tiled.
</TD></TR><TR><TD>
-gingham3
</TD><TD>
A slightly more complicated gingham. Can be tiled.
</TD></TR><TR><TD>
-madras
</TD><TD>
A madras plaid. Can be tiled.
</TD></TR><TR><TD>
-tartan
</TD><TD>
A tartan plaid. Can be tiled.
</TD></TR><TR><TD>
-poles
</TD><TD>
Color gradients centered on randomly placed poles. May need to be run through
ppmquant.
</TD></TR><TR><TD>
-squig
</TD><TD>
Squiggly tubular pattern. Can be tiled. May need to be run through
ppmquant.
</TD></TR><TR><TD>
-camo
</TD><TD>
Camouflage pattern. May need to be run through
ppmquant.
</TD></TR><TR><TD>
-anticamo
</TD><TD>
Anticamouflage pattern; like
-camo, but ultra-bright colors. May need to be run through
ppmquant.
</TD></TR></TABLE>
<P>All flags can be abbreviated to their shortest unique prefix.
</P>
<P><B>
REFERENCES
</B>
</P>
<P>Some of the patterns are from "Designer's Guide to Color 3" by Jeanne Allen.
</P>
<P><B>
SEE ALSO
</B>
</P>
<!-- CODE SNIP //-->
<PRE>pnmtile(1), ppmquant(1), ppm(5)
</PRE>
<!-- END CODE SNIP //-->
<A NAME="PAGENUM-411"><P>Page 411</P></A>
<P><B>
AUTHOR
</B></P>
<P>Copyright" 1989 by Jef Poskanzer.
</P>
<P>4 September 1989
</P>
<H3><A NAME="ch01_ 306">
ppmquant
</A></H3>
<P>ppmquant—Quantize the colors in a portable pixmap down to a specified number
</P>
<P><B>
SYNOPSIS
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
ppmquant [-floyd|-fs] ncolors [ppmfile]
ppmquant [-floyd|-fs] -map mapfile [ppmfile]
</PRE>
<!-- END CODE SNIP //-->
<P><B>
DESCRIPTION
</B>
</P>
<P>ppmquant reads a portable pixmap as input. It chooses
ncolors colors to best represent the image, maps the existing colors
to the new ones, and writes a portable pixmap as output.
</P>
<P>The quantization method is Heckbert's "median cut."
</P>
<P>Alternately, you can skip the color-choosing step by specifying your own set of colors with the
-map flag. The mapfile is just a ppm file; it can be any shape, all that matters is the colors in it. For instance, to quantize down to the 8-color IBM
TTL color set, you might use the following:
</P>
<!-- CODE //-->
<PRE>
P3
8 1
255
0 0 0
255 0 0
0 255 0
0 0 255
255 255 0
255 0 255
0 255 255
255 255 255
</PRE>
<!-- END CODE //-->
<P>If you want to quantize one pixmap to use the colors in another one, just use the second one as the mapfile. You don't
have to reduce it down to only one pixel of each color, just use it as is.
</P>
<P>The -floyd/-fs flag enables a Floyd-Steinberg error diffusion step. Floyd-Steinberg gives vastly better results on
images where the unmodified quantization has banding or other artifacts, especially when going to a small number of colors such
as the preceding IBM set. However, it does take substantially more CPU time, so the default is
off.
</P>
<P>All flags can be abbreviated to their shortest unique prefix.
</P>
<P><B>
REFERENCES
</B>
</P>
<P>"Color Image Quantization for Frame Buffer Display," by Paul Heckbert,
SIGGRAPH '82 Proceedings, page 297.
</P>
<P><B>
SEE ALSO
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
ppmquantall(1), pnmdepth(1), ppmdither(1), ppm(5)
</PRE>
<!-- END CODE SNIP //-->
<P><B>
AUTHOR
</B>
</P>
<P>Copyright" 1989, 1991 by Jef Poskanzer.
</P>
<P>12 January 1991
</P>
<P><CENTER>
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