[GEOS-8249]: heterogeneous resolution coverageView completion

doc/en/user/source/data/raster/coverageview.rst

@@ -3,24 +3,24 @@
 Coverage Views
 ==============
 
-Starting with GeoServer 2.6.0, You can define a new raster layer as a Coverage View.  
+Starting with GeoServer 2.6.0, You can define a new raster layer as a Coverage View.
 Coverage Views allow defining a View made of different bands originally available inside coverages (either bands of the same coverage or different coverages) of the same Coverage Store.
 
 Creating a Coverage View
 ------------------------
 
-In order to create a Coverage View the administrator invokes the :guilabel:`Create new layer` page. 
-When a Coverage store is selected, the usual list of coverages available for publication appears. 
+In order to create a Coverage View the administrator invokes the :guilabel:`Create new layer` page.
+When a Coverage store is selected, the usual list of coverages available for publication appears.
 A link :guilabel:`Configure new Coverage view...` also appears:
 
 .. figure:: images/coverageviewnewlayer.png
    :align: center
-   
+
 Selecting the :guilabel:`Configure new Coverage view...` link opens a new page where you can configure the coverage view:
 
 .. figure:: images/newcoverageview.png
    :align: center
-   
+
 The upper text box allows to specify the name to be assigned to this coverage view. (In the following picture we want to create as example, a **currents** view merging together both u and v components of the currents, which are exposed as separated 1band coverages).
 
 .. figure:: images/coverageviewname.png
@@ -32,7 +32,7 @@ It is possible to specify which input coverage bands need to be put on the view
 .. figure:: images/coverageviewselectbands.png
    :align: center
 
-Once selected, they needs to be added to the output bands of the coverage view, using the :guilabel:`add` button. 
+Once selected, they needs to be added to the output bands of the coverage view, using the :guilabel:`add` button.
 
 .. figure:: images/coverageviewaddbands.png
    :align: center
@@ -59,6 +59,31 @@ Once all the properties of the layer have been configured, by selecting the :gui
 .. figure:: images/coverageviewavailablelayers.png
    :align: center
 
+Heterogeneous coverage views
+----------------------------
+
+In case the various coverages bound in the view have different resolution, the UI will present
+two extra controls:
+
+.. figure:: images/coverageviewhetero.png
+   :align: center
+
+The **coverage envelope policy** defines how the bounding box of the output is calculated for metadata
+purposes. Having different resolutions, the coverages are unlikely to share the same bounding box. The possible values are:
+
+* **Intersect envelopes**: Use the intersection of all input coverage envelopes
+* **Union envelopes**: Use the union of all input coverage envelopes
+
+The **coverage resolution policy** defines which target resolution is used when generating outputs:
+
+* **Best**: Use the best resolution available among the chosen bands (e.g., in a set having 60m, 20m and 10m the 10m resolution will be chosen)
+* **Worst**: Use the worst resolution available among the chosen bands (e.g., in a set having 60m, 20m and 10m the 60m resolution will be chosen)
+
+The coverage resolution policy is *context sensitive*. Assume the input is a 12 bands Sentinel 2 dataset at three different
+resolution, 10, 20 and 30 meters, and a false color image is generated by performing a band selection in the SLD.
+If the policy is *best* and the SLD selects only bands at 20 and 60 meters, the output will be at 20 meters instead of
+10 meters.
+
 Coverage View in action
 -----------------------
 
@@ -67,4 +92,3 @@ the values of the bands composing the coverage view.
 
 .. figure:: images/coverageviewlayerpreview.png
    :align: center
-

src/main/src/main/java/org/geoserver/catalog/CoverageView.java

@@ -48,7 +48,7 @@ public static enum EnvelopeCompositionType {
      * Which Resolution to be used in composition
      */
     public static enum SelectedResolution {
-        BEST, WORST, INDEX;
+        BEST, WORST;
     }
 
     /**

src/main/src/main/java/org/geoserver/catalog/CoverageViewHandler.java

@@ -14,14 +14,15 @@
 import org.geoserver.catalog.CoverageView.EnvelopeCompositionType;
 import org.geoserver.catalog.CoverageView.InputCoverageBand;
 import org.geoserver.catalog.CoverageView.SelectedResolution;
+import org.geotools.coverage.grid.GridCoverage2D;
 import org.geotools.coverage.grid.GridEnvelope2D;
 import org.geotools.coverage.grid.io.GridCoverage2DReader;
 import org.geotools.coverage.grid.io.OverviewPolicy;
 import org.geotools.data.DataSourceException;
 import org.geotools.geometry.GeneralEnvelope;
-import org.geotools.geometry.jts.ReferencedEnvelope;
 import org.geotools.referencing.CRS;
 import org.geotools.referencing.operation.builder.GridToEnvelopeMapper;
+import org.geotools.referencing.operation.transform.AffineTransform2D;
 import org.geotools.referencing.operation.transform.ProjectiveTransform;
 import org.opengis.coverage.grid.GridEnvelope;
 import org.opengis.parameter.ParameterDescriptor;
@@ -38,18 +39,55 @@
 class CoverageViewHandler {
 
     /**
+     * Visit the a coverage and decide if its resolution is better than the ones
+     * previously visited
+     */
+    abstract static class CoverageResolutionChooser {
+
+        double[] resolution;
+
+        boolean visit(GridCoverage2D coverage) throws IOException {
+            MathTransform2D mt = coverage.getGridGeometry().getGridToCRS2D();
+            // cannot do a comparison
+            if (!(mt instanceof AffineTransform2D)) {
+                return false;
+            }
+            AffineTransform2D at = (AffineTransform2D) mt;
+            double scaleX = Math.abs(at.getScaleX());
+            double scaleY = Math.abs(at.getScaleY());
+            if (resolution == null) {
+                this.resolution = new double[2];
+                this.resolution[0] = scaleX;
+                this.resolution[1] = scaleY;
+                return true;
+            }
+            if (compare(scaleX, scaleY, resolution)) {
+                this.resolution[0] = scaleX;
+                this.resolution[1] = scaleY;
+                return true;
+            } else {
+                return false;
+            }
+        }
+
+        protected abstract boolean compare(double scaleX, double scaleY, double[] resolution);
+    }
+
+        /**
      * Visit the reader for a coverage composing the view 
      * and compute the resolution levels
      */
-    interface ResolutionComposer {
+    interface ReaderResolutionComposer {
         void visit(GridCoverage2DReader reader) throws IOException;
 
         double[][] getResolutionLevels();
 
         String getReferenceName();
+
+        CoverageResolutionChooser getCoverageResolutionChooser();
     }
 
-    abstract class AbstractResolutionComposer implements ResolutionComposer {
+    abstract class AbstractReaderResolutionComposer implements ReaderResolutionComposer {
         double[][] resolution;
 
         String referenceName = null;
@@ -68,7 +106,7 @@ public String getReferenceName() {
     /**
      * Implementation returning the Best resolution of the visited elements
      */
-    class BestResolutionComposer extends AbstractResolutionComposer {
+    class BestReaderResolutionComposer extends AbstractReaderResolutionComposer {
 
         @Override
         public void visit(GridCoverage2DReader reader) throws IOException {
@@ -83,12 +121,23 @@ public void visit(GridCoverage2DReader reader) throws IOException {
                 }
             }
         }
+
+        @Override
+        public CoverageResolutionChooser getCoverageResolutionChooser() {
+            return new CoverageResolutionChooser() {
+                @Override
+                protected boolean compare(double scaleX, double scaleY, double[] resolution) {
+                    return scaleX < resolution[0] && scaleY < resolution[1];
+                }
+            };
+        }
+
     }
 
     /**
      * Implementation returning the Worst resolution of the visited elements
      */
-    class WorstResolutionComposer extends AbstractResolutionComposer {
+    class WorstReaderResolutionComposer extends AbstractReaderResolutionComposer {
 
         @Override
         public void visit(GridCoverage2DReader reader) throws IOException {
@@ -103,33 +152,18 @@ public void visit(GridCoverage2DReader reader) throws IOException {
                 }
             }
         }
-    }
-
-    /**
-     * Implementation returning the resolution of the i-tx coverage of the view  
-     */
-    class IndexedResolutionComposer extends AbstractResolutionComposer {
-
-        private int selectedResolutionIndex;
-
-        private int visited = -1;
-
-        public IndexedResolutionComposer(int selectedResolutionIndex) {
-            this.selectedResolutionIndex = selectedResolutionIndex;
-        }
 
         @Override
-        public void visit(GridCoverage2DReader reader) throws IOException {
-            visited++;
-            if (visited == selectedResolutionIndex) {
-                resolution = reader.getResolutionLevels();
-                referenceName = reader.getGridCoverageNames()[0];
-            }
+        public CoverageResolutionChooser getCoverageResolutionChooser() {
+            return new CoverageResolutionChooser() {
+                @Override
+                protected boolean compare(double scaleX, double scaleY, double[] resolution) {
+                    return scaleX > resolution[0] && scaleY > resolution[1];
+                }
+            };
         }
     }
 
-    //TODO: Add support for imposed Resolution
-
     /**
      * Visit the reader for a coverage composing the view and compute the envelope.
      */
@@ -334,12 +368,12 @@ public boolean checkConsistency(GridCoverage2DReader reader) throws IOException
     /** The coverageView definition */
     private CoverageView coverageView;
 
-    private ResolutionComposer resolutionComposer;
+    private ReaderResolutionComposer resolutionComposer;
 
     private EnvelopeComposer envelopeComposer;
 
     public CoverageViewHandler(boolean supportHeterogeneousCoverages, GridCoverage2DReader delegate,
-            String referenceName, CoverageView coverageView) {
+                                     String referenceName, CoverageView coverageView) {
         this.supportHeterogeneousCoverages = supportHeterogeneousCoverages;
         this.delegate = delegate;
         this.referenceName = referenceName;
@@ -409,10 +443,6 @@ public GridEnvelope getOriginalGridRange() {
 
     }
 
-    public String getReferenceName() {
-        return referenceName;
-    }
-
     public MathTransform getOriginalGridToWorld(PixelInCell pixInCell) {
         if (homogeneousCoverages) {
             return delegate.getOriginalGridToWorld(referenceName, pixInCell);
@@ -436,17 +466,15 @@ public MathTransform getOriginalGridToWorld(PixelInCell pixInCell) {
     }
 
 
-    private ResolutionComposer initResolutionComposer() {
+    private ReaderResolutionComposer initResolutionComposer() {
         SelectedResolution selectedResolution = coverageView.getSelectedResolution();
         switch (selectedResolution) {
         case WORST:
-            return new WorstResolutionComposer();
+            return new WorstReaderResolutionComposer();
         case BEST:
-            return new BestResolutionComposer();
-        case INDEX:
-            return new IndexedResolutionComposer(coverageView.getSelectedResolutionIndex());
+            return new BestReaderResolutionComposer();
         default:
-            return new BestResolutionComposer();
+            return new BestReaderResolutionComposer();
         }
     }
 
@@ -464,14 +492,14 @@ private EnvelopeComposer initEnvelopeComposer() {
 
     public double[] getReadingResolutions(OverviewPolicy policy, double[] requestedResolution)
             throws IOException {
-        // TODO
-        if (homogeneousCoverages) {
-            return delegate.getReadingResolutions(referenceName, policy, requestedResolution);
-        }
         return delegate.getReadingResolutions(referenceName, policy, requestedResolution);
     }
 
     EnvelopeCompositionType getEnvelopeCompositionType() {
         return coverageView.getEnvelopeCompositionType();
     }
+
+    CoverageResolutionChooser getCoverageResolutionChooser() {
+        return resolutionComposer.getCoverageResolutionChooser();
+    }
 }