/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 2010, Open Source Geospatial Foundation (OSGeo)
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*/
package org.geotools.grid;
import org.geotools.geometry.jts.ReferencedEnvelope;
/**
* A helper class to create bounding envelopes with width and height that are
* simple multiples of a given resolution.
* <pre><code>
* // Example of use: creating an envlope with 'neat' lat-lon bounds
* // that encompasses a set of features
*
* SimpleFeatureSource featureSource = ...
* ReferencedEnvelope featureBounds = featureSource.getBounds();
* ReferencedEnvelope latLonEnv = featureBounds.transform(DefaultGeographicCRS.WGS84, true);
*
* // 1 degree grid resoluation
* final double gridSize = 1.0;
* ReferencedEnvelope gridBounds = Envelopes.expandToInclude(latLonEnv, gridSize);
* </code></pre>
*
* @todo move this class or its methods to a more general module
*
* @author mbedward
* @since 2.7
*
*
* @source $URL$
* @version $Id$
*/
public class Envelopes {
private static final double EPS = 1.0E-8;
/**
* Include the provided envelope, expanding as necessary and rounding
* the bounding coordinates such that they are multiples of the
* specified resolution. For example, if {@code resolution} is 100 then the
* min and max bounding coordinates of this envelope will set to mutliples
* of 100 by rounding down the min values and rounding up the max values
* if required.
* <pre><code>
* // Example, create a new envelope that cntains an input envlope and
* // whose boundind coordinates are multiples of 100
* //
* ReferencedEnvelope inputEnv = ...
* ReferencedEnvelope roundedEnv = new ReferencedEnvelope();
* roundedEnv.expandToInclude(inputEnv, 100);
* </code></pre>
*
* @param srcEnv the envelope to include
* @param resolution resolution (in world distance units) of the resulting
* boundary coordinates
*
* @return a new envelope with 'rounded' bounding coordinates
*/
public static ReferencedEnvelope expandToInclude(ReferencedEnvelope srcEnv, double resolution) {
double minX = roundOrdinate(srcEnv.getMinX(), resolution, false);
double maxX = roundOrdinate(srcEnv.getMaxX(), resolution, true);
double minY = roundOrdinate(srcEnv.getMinY(), resolution, false);
double maxY = roundOrdinate(srcEnv.getMaxY(), resolution, true);
ReferencedEnvelope expanded = new ReferencedEnvelope(srcEnv);
expanded.expandToInclude(minX, minY);
expanded.expandToInclude(maxX, maxY);
return expanded;
}
/**
* Helper method to round ordinate values up or down to a specified resolution.
* The returned value will be a multiple of the specified resolution.
* <pre><code>
* double ordinate = 1234.56;
* double resolution = 100;
* double rounded;
*
* // this will return 1200
* rounded = roundOrdinate(ordinate, resolution, false);
*
* // this will return 1300
* rounded = roundOrdinate(ordinate, resolution, true);
* </code></pre>
* @param ordinate the ordinate to round up or down.
* @param resolution the desired resolution
* @param roundUp true to round up; false to round down
*
* @return the rounded ordinate value
*/
private static double roundOrdinate(double ordinate, double resolution, boolean roundUp) {
double unsigned = Math.abs(ordinate);
boolean negative = ordinate < 0.0;
if (negative) {
roundUp = !roundUp;
}
double rounded;
if (roundUp) {
double x = unsigned / resolution;
int up = (x - (long) x) > EPS ? 1 : 0;
rounded = resolution * (up + (long) x);
} else {
rounded = resolution * (long) (unsigned / resolution);
}
return negative ? -rounded : rounded;
}
}