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<a href="0368-0370.html">Previous</A> | <a href="../ewtoc.html">Table of Contents</A> | <a href="0375-0377.html">Next</A></CENTER></P>
<A NAME="PAGENUM-371"><P>Page 371</P></A>
<P><B>
AUTHOR
</B></P>
<P>John Walker<BR>
Autodesk SA Avenue des Champs-Montants 14b<BR>
CH-2074 MARIN<BR>
Suisse/Schweiz/Svizzera/Svizra/Switzerland
</P>
<TABLE>
<TR><TD>
Usenet:
</TD><TD>
kelvin@Autodesk.com
</TD></TR><TR><TD>
Fax:
</TD><TD>
038/33 88 15
</TD></TR><TR><TD>
Voice:
</TD><TD>
038/33 76 33
</TD></TR></TABLE>
<P>Permission to use, copy, modify, and distribute this software and its documentation for any purpose and without fee
is hereby granted, without any conditions or restrictions. This software is provided "as is" without express or implied warranty.
</P>
<P>PLUGWARE! If you like this kind of stuff, you may also enjoy James Gleick's "Chaos—The Software" for
MS-DOS, available for $59.95 from your local software store or directly from Autodesk, Inc., Attn: Science Series, 2320
Marinship Way, Sausalito, CA 94965, USA. Telephone: 800-688-2344 toll-free or, outside the U.S. (415) 332-2344 Ext 4886.
Fax: 415-289-4718. "Chaos—The Software" includes a more comprehensive fractal forgery generator that creates
three-dimensional landscapes as well as clouds and planets, plus five more modules that explore other aspects of Chaos. The
user guide of more than 200 pages includes an introduction by James Gleick and detailed explanations by Rudy Rucker of
the mathematics and algorithms used by each program.
</P>
<P>15 October 1991
</P>
<H3><A NAME="ch01_ 241">
pgmedge
</A></H3>
<P>pgmedge—Edge detect a portable graymap
</P>
<P><B>
SYNOPSIS
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
pgmedge [pgmfile]
</PRE>
<!-- END CODE SNIP //-->
<P><B>
DESCRIPTION
</B>
</P>
<P>pgmedge reads a portable graymap as input, outlines the edges, and writes a portable graymap as output. Piping the
result through pgmtopbm -threshold and playing with the threshold value will give a bitmap of the edges.
</P>
<P>The edge detection technique used is to take the Pythagorean sum of two Sobel gradient operators at 90 degrees to
each other. For more details see Digital Image
Processing by Gonzalez and Wintz, Chapter 7.
</P>
<P><B>
SEE ALSO
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
pgmenhance(1), pgmtopbm(1), pgm(5), pbm(5)
</PRE>
<!-- END CODE SNIP //-->
<P><B>
AUTHOR
</B>
</P>
<P>Copyright " 1991 by Jef Poskanzer.
</P>
<P>4 February 1990
</P>
<H3><A NAME="ch01_ 242">
pgmenhance
</A></H3>
<P>pgmenhance—Edge enhance a portable graymap
</P>
<P><B>
SYNOPSIS
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
pgmenhance [-N][pgmfile]
</PRE>
<!-- END CODE SNIP //-->
<A NAME="PAGENUM-372"><P>Page 372</P></A>
<P><B>
DESCRIPTION
</B>
</P>
<P>pgmenhance reads a portable graymap as input, enhances the edges, and writes a portable graymap as output.
</P>
<P>The edge enhancing technique is taken from Philip R. Thompson's
xim program, which took it from section 6 of
Digital Halftones by Dot Diffusion, D. E. Knuth, ACM Transaction on
Graphics Vol. 6, No. 4, October 1987, which in turn got
it from two 1976 papers by J. F. Jarvis et. al.
</P>
<P><B>
OPTIONS
</B>
</P>
<P>The optional -N flag should be a digit from 1 to 9. 1 is the lowest level of enhancement, 9 is the highest; the default is 9.
</P>
<P><B>
SEE ALSO
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
pgmedge(1), pgm(5), pbm(5)
</PRE>
<!-- END CODE SNIP //-->
<P><B>
AUTHOR
</B>
</P>
<P>Copyright " 1989 by Jef Poskanzer.
</P>
<P>13 January 1989
</P>
<H3><A NAME="ch01_ 243">
pgmhist
</A></H3>
<P>pgmhist—Print a histogram of the values in a portable graymap
</P>
<P><B>
SYNOPSIS
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
pgmhist [pgmfile]
</PRE>
<!-- END CODE SNIP //-->
<P><B>
DESCRIPTION
</B>
</P>
<P>pgmhist reads a portable graymap as input and prints a histogram of the gray values.
</P>
<P><B>
SEE ALSO
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
pgmnorm(1), pgm(5), ppmhist(1)
</PRE>
<!-- END CODE SNIP //-->
<P><B>
AUTHOR
</B>
</P>
<P>Copyright " 1989 by Jef Poskanzer
</P>
<P>28 February 1989
</P>
<H3><A NAME="ch01_ 244">
pgmkernel
</A></H3>
<P>pgmkernel—Generate a convolution kernel
</P>
<P><B>
SYNOPSIS
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
pgmkernel [ _weight w ] width [ height ]
</PRE>
<!-- END CODE SNIP //-->
<P><B>
DESCRIPTION
</B>
</P>
<P>pgmkernel generates a portable graymap array of size
width x height (or width x width if height is not specified) to be used
as a convolution file by pnmconvol. The data in the convolution array K are computed according to the formula:
</P>
<A NAME="PAGENUM-373"><P>Page 373</P></A>
<P>where w is a coefficient specified via the _weight
flag, and width and height are the X and Y filter sizes.
</P>
<P>The output PGM file is always written out in ASCII format.
</P>
<P><B>
OPTIONS
</B>
</P>
<P>The optional -weight flag should be a real number greater than -1. The default value is
6.0.
</P>
<P><B>
BUGS
</B>
</P>
<P>The computation time is proportional to width *
height. This increases rapidly with the increase of the kernel size. A
better approach could be to use a FFT in these cases.
</P>
<P><B>
SEE ALSO
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
pnmconvol(1), pnmsmooth(1)
</PRE>
<!-- END CODE SNIP //-->
<P><B>
AUTHOR
</B>
</P>
<P>Alberto Accomazzi (alberto@cfa.harvard.edu)
</P>
<P>10 December 1992
</P>
<H3><A NAME="ch01_ 245">
pgmnoise
</A></H3>
<P>pgmnoise—Create a graymap made up of white noise
</P>
<P><B>
SYNOPSIS
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
pgmnoise width height
</PRE>
<!-- END CODE SNIP //-->
<P><B>
DESCRIPTION
</B>
</P>
<P>pgmnoise creates a portable graymap that is made up of random pixels with gray values in the range of
0 to PGM_MAXMAXVAL (depends on the compilation, either
255 or 65535). The graymap has a size of width *
height pixels.
</P>
<P><B>
SEE ALSO
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
pgm(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_ 246">
pgmnorm
</A></H3>
<P>pgmnorm—Normalize the contrast in a portable graymap
</P>
<P><B>
SYNOPSIS
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
pgmnorm[-bpercent N | -bvalue N][-wpercent N | -wvalue N][pgmfile]
</PRE>
<!-- END CODE SNIP //-->
<P><B>
DESCRIPTION
</B>
</P>
<P>pgmnorm reads a portable graymap 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 graymap as output.
</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
</P>
<A NAME="PAGENUM-374"><P>Page 374</P></A>
<P>
mapped by using the -bvalue and -wvalue flags. Appropriate numbers for the flags can be gotten from the
pgmhist 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>
pgmhist(1), ppmnorm(1), pgm(5)
</PRE>
<!-- END CODE SNIP //-->
<P><B>
AUTHOR
</B>
</P>
<P>Partially based on the fbnorm filter in Michael Mauldin's "Fuzzy Pixmap" package.
</P>
<P>Copyright" 1989 by Jef Poskanzer.
</P>
<P>28 February 1989
</P>
<H3><A NAME="ch01_ 247">
pgmoil
</A></H3>
<P>pgmoil—Turn a portable graymap into an oil painting
</P>
<P><B>
SYNOPSIS
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
pgmoil [-n N][pgmfile]
</PRE>
<!-- END CODE SNIP //-->
<P><B>
DESCRIPTION
</B>
</P>
<P>pgmoil reads a portable graymap as input, does an "oil transfer," and writes a portable graymap as output.
</P>
<P>The oil transfer is described in Beyond
Photography by Holzmann, Chapter 4, photo 7. It's a sort of localized smearing.
</P>
<P><B>
OPTIONS
</B>
</P>
<P>The optional -n flag controls the size of the area smeared. The default value is
3.
</P>
<P><B>
BUGS
</B>
</P>
<P>Takes a long time to run.
</P>
<P><B>
SEE ALSO
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
pgmbentley(1), ppmrelief(1), pgm(5)
</PRE>
<!-- END CODE SNIP //-->
<P><B>
AUTHOR
</B>
</P>
<P>Copyright" 1990 by Wilson Bent
(whb@hoh-2.att.com).
</P>
<P>11 January 1991
</P>
<H3><A NAME="ch01_ 248">
pgmramp
</A></H3>
<P>pgmramp—Generate a grayscale ramp
</P>
<P><B>
SYNOPSIS
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
pgmramp -lr|-tb | -rectangle|-ellipse width height
</PRE>
<!-- END CODE SNIP //-->
<P><B>
DESCRIPTION
</B>
</P>
<P>pgmramp generates a graymap of the specified size containing a black-to-white ramp. These ramps are useful for
multiplying with other images, using the pnmarith tool.
</P>
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