jiayuasu commented on code in PR #973:
URL: https://github.com/apache/sedona/pull/973#discussion_r1295524162
##########
common/src/main/java/org/apache/sedona/common/raster/GeometryFunctions.java:
##########
@@ -61,6 +63,70 @@ public static Geometry convexHull(GridCoverage2D raster)
throws FactoryException
return geometryFactory.createPolygon(new Coordinate[] {coordOne,
coordTwo, coordThree, coordFour, coordOne});
}
+ public static Geometry minConvexHull(GridCoverage2D raster, Integer band)
throws FactoryException, TransformException {
+ boolean allBands = band == null;
+ if (!allBands) ensureSafeBand(raster, band);
+ int width = RasterAccessors.getWidth(raster), height =
RasterAccessors.getHeight(raster), srid = RasterAccessors.srid(raster);
+ int minX = Integer.MAX_VALUE, maxX = Integer.MIN_VALUE, minY =
Integer.MAX_VALUE, maxY = Integer.MIN_VALUE;
+ for (int j = 0; j < height; j++) {
+ for (int i = 0; i < width; i++) {
+ // get the value of the raster at the coordinates i, j
+ //if value is not no data, update variables to track minX,
maxX, minY, maxY
+ GridCoordinates2D currGridCoordinate = new
GridCoordinates2D(i, j);
+ double[] bandPixelValues = raster.evaluate(currGridCoordinate,
(double[]) null);
+ if (allBands) {
Review Comment:
The duplicate code here can be merged. You can use the same for loop for
both condition by manually controlling the start and end of this loop.
##########
common/src/test/java/org/apache/sedona/common/raster/GeometryFunctionsTest.java:
##########
@@ -76,6 +77,49 @@ public void testConvexHullFromRasterFile() throws
FactoryException, TransformExc
assertEquals(expectedCoordOne.getY(), coordinates[4].getY(), 0.5d);
}
+ @Test
+ public void testMinConvexHull() throws FactoryException,
TransformException {
Review Comment:
Do these tests yield the same results as PostGIS?
##########
docs/api/sql/Raster-operators.md:
##########
@@ -62,14 +62,70 @@ Since: `1.5.0`
Spark SQL example:
```sql
-SELECT RS_ConvexHull(SELECT RS_PixelAsPoint(RS_MakeEmptyRaster(1, 5, 10, 156,
-132, 5, 10, 3, 5, 0)));
+SELECT RS_ConvexHull(RS_MakeEmptyRaster(1, 5, 10, 156, -132, 5, 10, 3, 5, 0));
```
Output:
```
POLYGON ((156 -132, 181 -107, 211 -7, 186 -32, 156 -132))
```
+### RS_MinConvexHull
+
+Introduction: Returns the min convex hull geometry of the raster **excluding**
the NoDataBandValue band pixels, in the given band.
Review Comment:
Please also add that the produced geometry uses the world coordinate in the
CRS specified by the raster.
##########
common/src/main/java/org/apache/sedona/common/raster/GeometryFunctions.java:
##########
@@ -61,6 +63,70 @@ public static Geometry convexHull(GridCoverage2D raster)
throws FactoryException
return geometryFactory.createPolygon(new Coordinate[] {coordOne,
coordTwo, coordThree, coordFour, coordOne});
}
+ public static Geometry minConvexHull(GridCoverage2D raster, Integer band)
throws FactoryException, TransformException {
+ boolean allBands = band == null;
+ if (!allBands) ensureSafeBand(raster, band);
+ int width = RasterAccessors.getWidth(raster), height =
RasterAccessors.getHeight(raster), srid = RasterAccessors.srid(raster);
+ int minX = Integer.MAX_VALUE, maxX = Integer.MIN_VALUE, minY =
Integer.MAX_VALUE, maxY = Integer.MIN_VALUE;
+ for (int j = 0; j < height; j++) {
+ for (int i = 0; i < width; i++) {
+ // get the value of the raster at the coordinates i, j
+ //if value is not no data, update variables to track minX,
maxX, minY, maxY
+ GridCoordinates2D currGridCoordinate = new
GridCoordinates2D(i, j);
+ double[] bandPixelValues = raster.evaluate(currGridCoordinate,
(double[]) null);
+ if (allBands) {
+ for (int currBand = 1; currBand <=
RasterAccessors.numBands(raster); currBand++) {
+ double currBandValue = bandPixelValues[currBand - 1];
+ Double bandNoDataValue =
RasterBandAccessors.getBandNoDataValue(raster, currBand);
+ if ((bandNoDataValue == null) || currBandValue !=
bandNoDataValue) {
Review Comment:
When there are multiple bands, is the overall minConvexHull the hull that
has the minX, minY, maxX, maxY among all bands?
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