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@@ -9,6 +9,7 @@ parameter), or like <em>r.buffer</em>, but with the
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option of preserving the original cells (similar to combining
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<em>r.buffer</em> and <em>r.patch</em>).
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+
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<h2>NOTES</h2>
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The user has the option of specifying three different metrics which
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control the geometry in which grown cells are created, (controlled by
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@@ -28,7 +29,6 @@ Cells grown using this metric would form isolines of distance that are
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circular from a given point, with the distance given by the <b>radius</b>.
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<p>
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-
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The <i>Manhattan metric</i>, or <i>Taxicab geometry</i>, is a form of geometry in
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which the usual metric of Euclidean geometry is replaced by a new
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metric in which the distance between two points is the sum of the (absolute)
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@@ -44,7 +44,6 @@ where cells grown using this metric would form isolines of distance that are
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rhombus-shaped from a given point.
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<p>
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-
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The <i>Maximum metric</i> is given by the formula
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<div class="code"><pre>d(dx,dy) = max(abs(dx),abs(dy))</pre></div>
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@@ -52,13 +51,29 @@ The <i>Maximum metric</i> is given by the formula
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where the isolines of distance from a point are squares.
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<p>
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-
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If there are two cells which are equal candidates to grow into an empty space,
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<em>r.grow</em> will choose the northernmost candidate; if there are multiple
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candidates with the same northing, the westernmost is chosen.
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-<h2>SEE ALSO</h2>
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+<h2>EXAMPLE</h2>
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+
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+You can shrink inwards by preparing an inverse map first, and then
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+inverting the resulting grown map. For example:
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+<div class="code"><pre>
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+# Spearfish sample dataset
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+
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+MAP=fields
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+g.region rast=$MAP
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+r.mapcalc "inverse = if(isnull($MAP), 1, null())"
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+r.grow in=inverse out=inverse.grown
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+r.mapcalc "$MAP.shrunken = if(isnull(inverse.grown), $MAP, null())"
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+r.colors $MAP.shrunken rast=$MAP
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+g.remove inverse,inverse.grown
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+</pre></div>
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+
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+
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+<h2>SEE ALSO</h2>
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<em>
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<a href="r.buffer.html">r.buffer</a>,<br>
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<a href="r.grow.distance.html">r.grow.distance</a>,<br>
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@@ -66,10 +81,10 @@ candidates with the same northing, the westernmost is chosen.
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</em>
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<p>
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-
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<em><a href="http://en.wikipedia.org/wiki/Euclidean_metric">Wikipedia Entry: Euclidean Metric</a></em><br>
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<em><a href="http://en.wikipedia.org/wiki/Manhattan_metric">Wikipedia Entry: Manhattan Metric</a></em>
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+
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<h2>AUTHORS</h2>
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Marjorie Larson,
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@@ -77,4 +92,5 @@ U.S. Army Construction Engineering Research Laboratory
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<p>
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Glynn Clements
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-<p><i>Last changed: $Date$</i>
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+<p>
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+<i>Last changed: $Date$</i>
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Hamish Bowman