|
@@ -3,10 +3,12 @@
|
|
|
<em>i.landsat.rgb</em> auto-balances and enhances the color channels of a
|
|
|
LANDSAT RGB image to provide a more natural color mixture. Only the color
|
|
|
table of each image band is modified, the base data remains untouched.
|
|
|
-<p>The module works by calculating a histogram for each color channel and
|
|
|
+<p>
|
|
|
+The module works by calculating a histogram for each color channel and
|
|
|
removing an adjustable amount of outliers from either end before recalibrating
|
|
|
the color scale with <em>r.colors</em>.
|
|
|
-<p>It will work with any 8-bit RGB imagery set and the script is easily modified
|
|
|
+<p>
|
|
|
+It will work with any 8-bit RGB imagery set and the script is easily modified
|
|
|
to work with other datasets of greater band-depth.
|
|
|
|
|
|
<h2>NOTES</h2>
|
|
@@ -15,24 +17,39 @@ Depending on the image, it may or may not be advantageous to use the <b>-p</b>
|
|
|
flag to preserve the relative color scaling. You will have to experiment
|
|
|
with the different options to find a setting that works best for your
|
|
|
particular imagery.
|
|
|
-<p>The <b>strength</b> option should generally be set in the 90-99 range. The
|
|
|
+<p>
|
|
|
+The <b>strength</b> option should generally be set in the 90-99 range. The
|
|
|
lower the number, the more saturated the image becomes. It represents the
|
|
|
percentage cut-off for the top end of the color histogram curve. The lower
|
|
|
end is fixed at 2% of the area under the curve.
|
|
|
-<p>For quicker execution of this module on large images you can achieve largely
|
|
|
+<p>
|
|
|
+For quicker execution of this module on large images you can achieve largely
|
|
|
similar results by switching to a coarser resolution before the running of
|
|
|
the module (using <em>g.region</em>) and then back to the original resolution
|
|
|
afterwards.
|
|
|
|
|
|
-
|
|
|
<h2>EXAMPLE</h2>
|
|
|
|
|
|
-North Carolina sample dataset:
|
|
|
+North Carolina sample dataset example:
|
|
|
+
|
|
|
<div class="code"><pre>
|
|
|
-g.region rast=lsat7_2002_10
|
|
|
-i.landsat.rgb blue=lsat7_2002_10 green=lsat7_2002_20 red=lsat7_2002_30
|
|
|
+g.region rast=lsat7_2002_10 -p
|
|
|
+d.rgb blue=lsat7_2002_10 green=lsat7_2002_20 red=lsat7_2002_30
|
|
|
+d.barscale at=55.312500,93.125000 bcolor=white tcolor=black -t
|
|
|
+
|
|
|
+i.landsat.rgb blue=lsat7_2002_10 green=lsat7_2002_20 red=lsat7_2002_30 strength=95
|
|
|
+d.rgb blue=lsat7_2002_10 green=lsat7_2002_20 red=lsat7_2002_30
|
|
|
+d.barscale at=55.312500,93.125000 bcolor=white tcolor=black -t
|
|
|
</pre></div>
|
|
|
|
|
|
+<center>
|
|
|
+<img src="i_landsat_rgb_uncorrected.jpg" alt="Uncorrected RGB composite of Landsat ETM channels B/G/R"><br>
|
|
|
+Uncorrected RGB composite of Landsat ETM channels B/G/R
|
|
|
+<p>
|
|
|
+<img src="i_landsat_rgb_corrected.jpg" alt="Color corrected RGB composite of Landsat ETM channels B/G/R"><br>
|
|
|
+Color corrected RGB composite of Landsat ETM channels B/G/R
|
|
|
+</center>
|
|
|
+
|
|
|
<h2>TODO</h2>
|
|
|
|
|
|
The <b>strength</b> option requires further refinement.
|
|
@@ -51,7 +68,7 @@ The <b>strength</b> option requires further refinement.
|
|
|
|
|
|
<h2>AUTHORS</h2>
|
|
|
|
|
|
-Markus Neteler<br>
|
|
|
+Markus Neteler, Trento, Italy<br>
|
|
|
M. Hamish Bowman, Dept. Marine Science, Otago University, New Zealand
|
|
|
|
|
|
<p><i>Last changed: $Date$</i>
|