[GRASS-SVN] r48366 - grass/branches/releasebranch_6_4/raster/r.texture

[svn_grass at osgeo.org]

Author: neteler
Date: 2011-09-19 12:25:38 -0700 (Mon, 19 Sep 2011)
New Revision: 48366

Modified:
   grass/branches/releasebranch_6_4/raster/r.texture/description.html
Log:
explain r.rescale; NC example added

Modified: grass/branches/releasebranch_6_4/raster/r.texture/description.html
===================================================================
--- grass/branches/releasebranch_6_4/raster/r.texture/description.html	2011-09-19 15:26:51 UTC (rev 48365)
+++ grass/branches/releasebranch_6_4/raster/r.texture/description.html	2011-09-19 19:25:38 UTC (rev 48366)
@@ -1,6 +1,6 @@
 <h2>DESCRIPTION</h2>
 
-<em>r.texture</em> - Creates map raster with textural features for
+<em>r.texture</em> creates raster maps with textural features from a
 user-specified raster map layer. The module calculates textural features 
 based on spatial dependence matrices at 0, 45, 90, and 135 
 degrees for a <em>distance</em> (default = 1).
@@ -8,17 +8,16 @@
 In general, several variables constitute texture: differences in grey level values,
 coarseness as scale of grey level differences, presence or lack of directionality
 and regular patterns.
-
 <p>
 <em>r.texture</em> reads a GRASS raster map as input and calculates textural 
 features based on spatial
 dependence matrices for north-south, east-west, northwest, and southwest
-directions using a side by side neighborhood (i.e., a distance of 1). Be
-sure to carefully set your resolution (using 
-<a href="g.region.html">g.region</a>) before running this program, or else your
-computer could run out of memory.  Also, make sure that your raster map has
-no more than 255 categories.  The output consists into four images for each
-textural feature, one for every direction.</p>
+directions using a side by side neighborhood (i.e., a distance of 1). The user
+should be sure to carefully set the resolution (using <em>g.region</em>) before
+running this program, or the computer may run out of memory. 
+The output consists into four images for each textural feature, one for every
+direction.
+
 <p>
 A commonly used texture model is based on the so-called grey level co-occurrence
 matrix. This matrix is a two-dimensional histogram of grey levels
@@ -77,8 +76,13 @@
 </ul>
    
 <h2>NOTES</h2>
-Algorithm taken from:<br>
 
+Importantly, the input raster map cannot have more than 255 categories. If needed,
+a map with more categories can be rescaled using <em>r.rescale</em>.
+
+<p>
+The algorithm was implemented after:<br>
+
 Haralick, R.M., K. Shanmugam, and I. Dinstein. 1973. Textural features for
     image classification. <em>IEEE Transactions on Systems, Man, and
     Cybernetics</em>, SMC-3(6):610-621.
@@ -105,15 +109,27 @@
 ortho_texture_ASM_0, ortho_texture_ASM_45, ortho_texture_ASM_90, ortho_texture_ASM_135.
 
 
-
-
 <h2>BUGS</h2>
 - The program can run incredibly slow for large raster maps.
 <p>
 - The method for finding the maximal correlation coefficient, which
     requires finding the second largest eigenvalue of a matrix Q, does not
-    always converge.
+    always converge. This is a known issue with this measure in general.
 
+
+<h2>EXAMPLE</h2>
+
+From the orthophoto in the North Carolina sample dataset, calculate
+Angular Second Moment and Sum Entropy texture measures:
+
+<div class="code"><pre>
+g.region rast=ortho_2001_t792_1m -p
+r.texture -ax ortho_2001_t792_1m prefix=ortho_texture
+r.info -r ortho_texture_ASM_135
+r.info -r ortho_texture_SV_90
+</pre></div>
+
+
 <h2>REFERENCES</h2>
 <b>Haralick, R.M., K. Shanmugam, and I. Dinstein</b> (1973). Textural features for
     image classification. <em>IEEE Transactions on Systems, Man, and
@@ -131,15 +147,16 @@
      
 <h2>SEE ALSO</h2>
 
-<em><a href="i.smap.html">i.smap</a></em>,
-<em><a href="i.gensigset.html">i.gensigset</a></em>,
-<em><a href="i.pca.html">i.pca</a></em>,
-<em><a href="r.digit.html">r.digit</a></em>,
-<em><a href="i.group.html">i.group</a></em>
+<em>
+<a href="i.smap.html">i.smap</a>,
+<a href="i.gensigset.html">i.gensigset</a>,
+<a href="i.pca.html">i.pca</a>,
+<a href="r.rescale.html">r.rescale</a>
+</em>
 
 <h2>AUTHOR</h2>
 <a href="mailto:antoniol at ieee.org">G. Antoniol</a> - RCOST (Research Centre on Software Technology - Viale Traiano - 82100 Benevento)<br>
-<a href="mailto:basco at unisannio.it">C. Basco</a> -  RCOST (Research Centre on Software Technology - Viale Traiano - 82100 Benevento)<br>
-<a href="mailto:ceccarelli at unisannio.it">M. Ceccarelli</a> - Facolta di Scienze, Universita del Sannio, Benevento
+C. Basco -  RCOST (Research Centre on Software Technology - Viale Traiano - 82100 Benevento)<br>
+M. Ceccarelli - Facolta di Scienze, Universita del Sannio, Benevento
 
-<p><i>Last changed: $Date$</i></p>
+<p><i>Last changed: $Date$</i>