📄 0375-0377.html
字号:
<HTML>
<HEAD>
<TITLE>Linux Complete Command Reference:User Commands:EarthWeb Inc.-</TITLE>
</HEAD>
<META NAME="ROBOTS" CONTENT="NOINDEX, NOFOLLOW">
<SCRIPT>
<!--
function displayWindow(url, width, height) {
var Win = window.open(url,"displayWindow",'width=' + width +
',height=' + height + ',resizable=1,scrollbars=yes');
}
//-->
</SCRIPT>
</HEAD>
-->
<!-- ISBN=0672311046 //-->
<!-- TITLE=Linux Complete Command Reference//-->
<!-- AUTHOR=Red Hat//-->
<!-- PUBLISHER=Macmillan Computer Publishing//-->
<!-- IMPRINT=Sams//-->
<!-- CHAPTER=01 //-->
<!-- PAGES=0001-0736 //-->
<!-- UNASSIGNED1 //-->
<!-- UNASSIGNED2 //-->
<P><CENTER>
<a href="0371-0374.html">Previous</A> | <a href="../ewtoc.html">Table of Contents</A> | <a href="0378-0380.html">Next</A></CENTER></P>
<A NAME="PAGENUM-375"><P>Page 375</P></A>
<P><B>
Options
</B></P>
<TABLE>
<TR><TD>
-lr
</TD><TD>
A left to right ramp
</TD></TR><TR><TD>
-tb
</TD><TD>
A top to bottom ramp
</TD></TR><TR><TD>
-rectangle
</TD><TD>
A rectangular ramp
</TD></TR><TR><TD>
-ellipse
</TD><TD>
An elliptical ramp
</TD></TR></TABLE>
<P>All flags can be abbreviated to their shortest unique prefix.
</P>
<P><B>
SEE ALSO
</B>
</P>
<P>pnmarith(1), pgm(5)
</P>
<P><B>
AUTHOR
</B>
</P>
<P>Copyright " 1989 by Jef Poskanzer.
</P>
<P>24 November 1989
</P>
<H3><A NAME="ch01_ 249">
pgmtexture
</A></H3>
<P>pgmtexture—Calculate textural features on a portable graymap
</P>
<P><B>
SYNOPSIS
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
pgmtexture [-d d][pgmfile]
</PRE>
<!-- END CODE SNIP //-->
<P><B>
DESCRIPTION
</B>
</P>
<P>pgmtexture reads a portable graymap as input. Calculates textural features based on spatial dependence matrices at 0, 45,
90, and 135 degrees for a distance d (default = 1). Textural features include
</P>
<TABLE>
<TR><TD>
(1)
Angular Second Moment
</TD><TD>
(2)
</TD></TR><TR><TD>
Contrast
</TD><TD>
</TD></TR><TR><TD>
(3)
</TD><TD>
Correlation
</TD></TR><TR><TD>
(4)
</TD><TD>
Variance
</TD></TR><TR><TD>
(5)
</TD><TD>
Inverse Difference Moment
</TD></TR><TR><TD>
(6)
</TD><TD>
Sum Average
</TD></TR><TR><TD>
(7)
</TD><TD>
Sum Variance
</TD></TR><TR><TD>
(8)
</TD><TD>
Sum Entropy
</TD></TR><TR><TD>
(9)
</TD><TD>
Entropy
</TD></TR><TR><TD>
(10)
</TD><TD>
Difference Variance
</TD></TR><TR><TD>
(11)
</TD><TD>
Difference Entropy
</TD></TR><TR><TD>
(12, 13)
</TD><TD>
Information Measures of Correlation
</TD></TR><TR><TD>
(14)
</TD><TD>
Maximal Correlation Coefficient
</TD></TR></TABLE>
<P>Algorithm taken from "Textural Features for Image Classification,"
IEEE Transactions on Systems, Man, and
Cybertinetics, R.M. Haralick, K. Shanmugam, and I. Dinstein, 1973. SMC-3(6):610_621.
</P>
<P><B>
BUGS
</B>
</P>
<P>The program can run incredibly slowly for large images (larger than
64¥64) and command-line options are limited.
The method for finding the maximal correlation coefficient, which requires finding the second largest
eigenvalue of a matrix Q, does not always converge.
</P>
<P><B>
REFERENCES
</B>
</P>
<P>IEEE Transactions on Systems, Man, and
Cybertinetics, SMC-3(6):610_621.
</P>
<A NAME="PAGENUM-376"><P>Page 376</P></A>
<P><B>
SEE ALSO
</B>
</P>
<!-- CODE SNIP //-->
<PRE>pgm(5), pnmcut(1)
</PRE>
<!-- END CODE SNIP //-->
<P><B>
AUTHOR
</B>
</P>
<P>Copyright " 1991 by Texas Agricultural Experiment Station, employer-for-hire of James Darrell McCauley.
</P>
<P>22 August 1991
</P>
<H3><A NAME="ch01_ 250">
pgmtofs
</A></H3>
<P>pgmtofs—Convert portable graymap to Usenix FaceSaver format
</P>
<P><B>
SYNOPSIS
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
pgmtofs [pgmfile]
</PRE>
<!-- END CODE SNIP //-->
<P><B>
DESCRIPTION
</B>
</P>
<P>pgmtofs reads a portable graymap as input. Produces Usenix FaceSaver format as output.
</P>
<P>FaceSaver is a registered trademark of Metron Computerware Ltd. of Oakland, CA.
</P>
<P><B>
SEE ALSO
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
fstopgm(1), pgm(5)
</PRE>
<!-- END CODE SNIP //-->
<P><B>
AUTHOR
</B>
</P>
<P>Copyright" 1991 by Jef Poskanzer.
</P>
<P>18 May 1990
</P>
<H3><A NAME="ch01_ 251">
pgmtolispm
</A></H3>
<P>pgmtolispm—Convert a portable graymap into Lisp machine format
</P>
<P><B>
SYNOPSIS
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
pgmtolispm [pgmfile]
</PRE>
<!-- END CODE SNIP //-->
<P><B>
DESCRIPTION
</B>
</P>
<P>pgmtolispm reads a portable graymap as input and produces a Lisp machine bitmap as output.
</P>
<P>This is the file format read by the
tv:read-bit-array-file function on TI Explorer and Symbolics Lisp machines.
</P>
<P>Given a PGM (instead of a PBM), a multiplane image will be output. This is probably not useful unless you have a
color Lisp machine.
</P>
<P>Multiplane bitmaps on Lisp machines are color; but the
lispm image file format does not include a colormap, so it must
be treated as a graymap instead. This is unfortunate.
</P>
<P><B>
SEE ALSO
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
lispmtopgm(1), pgm(5)
</PRE>
<!-- END CODE SNIP //-->
<P><B>
BUGS
</B>
</P>
<P>Output width is always rounded up to the nearest multiple of 32; this might not always be what you want, but it probably
is (arrays that are not modulo 32 cannot be passed to the
lispm BITBLT function, and thus cannot easily be displayed on the screen).
</P>
<P>No color.
</P>
<A NAME="PAGENUM-377"><P>Page 377</P></A>
<P><B>
Author
</B></P>
<P>Copyright " 1991 by Jamie Zawinski and Jef Poskanzer.
</P>
<P>6 March 1990
</P>
<H3><A NAME="ch01_ 252">
pgmtopbm
</A></H3>
<P>pgmtopbm—Convert a portable graymap into a portable bitmap
</P>
<P><B>
SYNOPSIS
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
pgmtopbm [-floyd|-fs|-threshold |-hilbert |-dither8|-d8|-cluster3
|-c3|-cluster4|-c4 |-cluster8|-c8][-value val][-clump size][pgmfile]
</PRE>
<!-- END CODE SNIP //-->
<P><B>
DESCRIPTION
</B>
</P>
<P>pgmtopbm reads a portable graymap as input and produces a portable bitmap as output.
</P>
<P>Note that there is no pbmtopgm converter because any
pgm program can read PBM files automagically.
</P>
<P><B>
OPTIONS
</B>
</P>
<P>The default quantization method is boustrophedonic Floyd-Steinberg error diffusion
(-floyd or -fs). Also available are simple thresholding
(-threshold); Bayer's ordered dither (-dither8) with a
16¥16 matrix; and three different sizes of 45-degree clustered-dot dither
(-cluster3, -cluster4, -cluster8). A space-filling curve halftoning method using the
Hilbert curve is also available. (-hilbert).
</P>
<P>Floyd-Steinberg will almost always give the best looking results; however, looking good is not always what you want.
For instance, thresholding can be used in a pipeline with the
pnmconvol tool, for tasks like edge and peak detection.
And clustered-dot dithering gives a newspaper-like look, a useful special effect. The
-value flag alters the thresholding value for Floyd-Steinberg and simple thresholding. It should be a real number between 0 and 1. Above 0.5 means darker
images; below 0.5 means lighter.
</P>
<P>The Hilbert curve method is useful for processing images before display on devices that do not render individual
pixels distinctly (like laser printers). This dithering method can give better results than the dithering usually done by the
laser printers themselves. The -clump flag alters the number of pixels in a clump. This is usually an integer between 2 and
100 (default 5). Smaller clump sizes smear the image less and are less grainy, but seem to loose some grayscale linearity.
Typically, a PGM image will have to be scaled to fit on a laser printer page (2400
¥ 3000 pixels for an A4 300dpi page), and
then dithered to a PBM image before being converted to a PostScript file. A printing pipeline might look something like this:
</P>
<!-- CODE SNIP //-->
<PRE>
pnmscale -xysize 2400 3000 image.pgm | pgmtopbm -hil | pnmtops -scale 0.25 image.ps
</PRE>
<!-- END CODE SNIP //-->
<P>All flags can be abbreviated to their shortest unique prefix.
</P>
<P><B>
REFERENCES
</B>
</P>
<P>The only reference you need for this stuff is Digital
Halftoning by Robert Ulichney, MIT Press, ISBN 0-262-21009-6.
</P>
<P>The Hilbert curve space filling method is taken from "Digital Halftoning with Space Filling Curves" by Luiz
Velho, Computer Graphics Volume 25, Number 4, proceedings of SIGRAPH '91, page 81. ISBN 0-89791-436-8
</P>
<P><B>
SEE ALSO
</B>
</P>
<!-- CODE SNIP //-->
<PRE>
pbmreduce(1), pgm(5), pbm(5), pnmconvol(1),
pnmscale(1), pnmtops(1)
</PRE>
<!-- END CODE SNIP //-->
<P><B>
AUTHOR
</B>
</P>
<P>Copyright " 1989 by Jef Poskanzer.
</P>
<P>26 July 1988
</P>
<P><CENTER>
<a href="0371-0374.html">Previous</A> | <a href="../ewtoc.html">Table of Contents</A> | <a href="0378-0380.html">Next</A></CENTER></P>
</td>
</tr>
</table>
<!-- begin footer information -->
</body></html>⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -