Merge pull request #1384 from ebocher/snaptogrid

SnapToGrid function

docs/CHANGELOG.md

@@ -1,4 +1,5 @@
 ## Changelog for v2.2.2
 - Read CPG file attached to the shapefile- 
 - Declare the schema for the spatial_ref_sys table
+- Add SnapToGrid function
 - Write empty geometry with the shapefile driver

h2gis-functions/src/main/java/org/h2gis/functions/factory/H2GISFunctions.java

@@ -62,6 +62,7 @@
 import org.h2gis.functions.spatial.generalize.ST_PrecisionReducer;
 import org.h2gis.functions.spatial.generalize.ST_Simplify;
 import org.h2gis.functions.spatial.generalize.ST_SimplifyPreserveTopology;
+import org.h2gis.functions.spatial.generalize.ST_SnapToGrid;
 import org.h2gis.functions.spatial.linear_referencing.ST_LineInterpolatePoint;
 import org.h2gis.functions.spatial.linear_referencing.ST_LineSubstring;
 import org.h2gis.functions.spatial.mesh.ST_ConstrainedDelaunay;
@@ -336,7 +337,8 @@ public static Function[] getBuiltInsFunctions() {
                 new ST_MinimumBoundingRadius(),
                 new ST_Project(),
                 new ST_IsProjectedCRS(),
-                new ST_IsGeographicCRS()
+                new ST_IsGeographicCRS(),
+                new ST_SnapToGrid()
         };
     }
 

h2gis-functions/src/main/java/org/h2gis/functions/spatial/generalize/ST_PrecisionReducer.java

@@ -55,6 +55,9 @@ public static Geometry precisionReducer(Geometry geometry, int nbDec) throws SQL
         if (geometry == null) {
             return null;
         }
+        if(nbDec==0){
+            return geometry;
+        }
         if (nbDec < 0) {
             throw new SQLException("Decimal_places has to be >= 0.");
         }

h2gis-functions/src/main/java/org/h2gis/functions/spatial/generalize/ST_SnapToGrid.java

@@ -0,0 +1,81 @@
+/**
+ * H2GIS is a library that brings spatial support to the H2 Database Engine
+ * <a href="http://www.h2database.com">http://www.h2database.com</a>. H2GIS is developed by CNRS
+ * <a href="http://www.cnrs.fr/">http://www.cnrs.fr/</a>.
+ *
+ * This code is part of the H2GIS project. H2GIS 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 3.0 of the License.
+ *
+ * H2GIS 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 <http://www.gnu.org/licenses/>.
+ *
+ *
+ * For more information, please consult: <a href="http://www.h2gis.org/">http://www.h2gis.org/</a>
+ * or contact directly: info_at_h2gis.org
+ */
+
+package org.h2gis.functions.spatial.generalize;
+
+import org.h2gis.api.DeterministicScalarFunction;
+import org.locationtech.jts.geom.Geometry;
+import org.locationtech.jts.geom.PrecisionModel;
+import org.locationtech.jts.precision.GeometryPrecisionReducer;
+
+import java.sql.SQLException;
+
+/**
+ * Function to snap a geometry according a grid size
+ * @author Erwan Bocher, CNRS, 2024
+ */
+public class ST_SnapToGrid extends DeterministicScalarFunction {
+
+    public ST_SnapToGrid() {
+        addProperty(PROP_REMARKS, "Snap all points of the input geometry to the grid defined by its origin and cell size.");
+    }
+
+    @Override
+    public String getJavaStaticMethod() {
+        return "execute";
+    }
+
+    /**
+     * Reduce the geometry precision. cell_size is resolution of grid to snap the points
+     *
+     * @param geometry
+     * @param cell_size
+     * @return
+     * @throws SQLException
+     */
+    public static Geometry execute(Geometry geometry, float cell_size) throws SQLException {
+        if (geometry == null) {
+            return null;
+        }
+        if(cell_size==0){
+            return geometry;
+        }
+        if (cell_size < 0) {
+            throw new SQLException("cell size has to be >= 0.");
+        }
+        PrecisionModel pm = new PrecisionModel(Math.round(1/cell_size));
+        GeometryPrecisionReducer geometryPrecisionReducer = new GeometryPrecisionReducer(pm);
+        try {
+            return geometryPrecisionReducer.reduce(geometry);
+        } catch (IllegalArgumentException ex) {
+            return geometry;
+        }
+    }
+
+    /**
+     * Computes the scale factor for a given number of decimal places.
+     *
+     * @param decimalPlaces
+     * @return the scale factor
+     */
+    public static double scaleFactorForDecimalPlaces(int decimalPlaces) {
+        return Math.pow(10.0, decimalPlaces);
+    }
+}

h2gis-functions/src/test/java/org/h2gis/functions/spatial/processing/ProcessingFunctionTest.java

@@ -317,6 +317,23 @@ public void test_ST_PrecisionReducer4() throws Exception {
         rs.close();
     }
 
+    @Test
+    public void test_ST_SnapToGrid1() throws Exception {
+        ResultSet rs = st.executeQuery("SELECT ST_SnapToGrid('LINESTRING(1.1115678 2.123, 4.111111 3.2374897, 4.11112 3.23748667)'::GEOMETRY, 0.001);");
+        rs.next();
+        assertGeometryEquals("LINESTRING(1.112 2.123,4.111 3.237)", rs.getBytes(1));
+        rs.close();
+    }
+
+    @Test
+    public void test_ST_SnapToGrid2() throws Exception {
+        ResultSet rs = st.executeQuery("SELECT ST_SnapToGrid('LINESTRINGZ(1.1115678 2.123 1, 4.111111 3.2374897 1, 4.11112 3.23748667 1)'::GEOMETRY, 0.001);");
+        rs.next();
+        assertGeometryEquals("LINESTRINGZ(1.112 2.123 1,4.111 3.237 1)", rs.getBytes(1));
+        rs.close();
+    }
+
+
     @Test
     public void test_ST_RingSideBuffer1() throws Exception {
         ResultSet rs = st.executeQuery("SELECT ST_RingSideBuffer('SRID=4326;LINESTRING (-10 10, 10 10)'::GEOMETRY, 10, 3);");