FilterFunction_gridCoverageStats.java

/* (c) 2013 - 2016 Open Source Geospatial Foundation - all rights reserved
 * This code is licensed under the GPL 2.0 license, available at the root
 * application directory.
 */
package org.geotools.process.raster;

import static org.geotools.filter.capability.FunctionNameImpl.parameter;
import it.geosolutions.imageio.pam.PAMDataset;
import it.geosolutions.imageio.pam.PAMDataset.PAMRasterBand;
import it.geosolutions.imageio.pam.PAMParser;

import org.geotools.coverage.grid.GridCoverage2D;
import org.geotools.filter.FunctionExpressionImpl;
import org.geotools.filter.capability.FunctionNameImpl;
import org.geotools.gce.imagemosaic.Utils;
import org.geotools.util.Utilities;
import org.opengis.filter.capability.FunctionName;

/**
 * Filter function to retrieve a grid coverage Stat value from the underlying GridCoverage2D
 * 
 * @author Daniele Romagnoli, GeoSolutions SAS
 */
public class FilterFunction_gridCoverageStats extends FunctionExpressionImpl {

    PAMParser pamParser = PAMParser.getInstance();

    public static FunctionName NAME = new FunctionNameImpl("gridCoverageStats",
            parameter("value", Number.class),
            parameter("property", String.class));

    public FilterFunction_gridCoverageStats() {
        super(NAME);
    }

    public Object evaluate(Object feature) {
        String arg0;

        try { // attempt to get value and perform conversion
            arg0 = (getExpression(0).evaluate(feature,String.class));
            Object val = null;
            if (feature instanceof GridCoverage2D) {
                GridCoverage2D coverage = (GridCoverage2D) feature;
                val = evaluate (coverage, arg0);
            }
            if (val != null) {
                return val;
            }
            throw new IllegalArgumentException("Filter Function problem for function gridCoverageStats: Unable to find the stat " 
                    + arg0 + " from the input object of type " + feature.getClass());
        } catch (Exception e) {
            // probably a type error
            throw new IllegalArgumentException("Filter Function problem for function gridCoverageStats", e);
        }
    }

    /**
     * Evaluating the filter function based on the provided coverage and the requested statName (minimum, maximum, ...)
     */
    public Object evaluate (final GridCoverage2D coverage, final String statName) {
        Utilities.ensureNonNull("coverage", coverage);
        final Object prop = coverage.getProperty(Utils.PAM_DATASET);
        if (prop != null && prop instanceof PAMDataset) {
            final PAMDataset dataset = (PAMDataset) prop;
            // Need to play with channel selection to deal with different raster bands
            final PAMRasterBand band = dataset.getPAMRasterBand().get(0);
            if (band != null) {
                final String value = pamParser.getMetadataValue(band, "STATISTICS_"+ statName.toUpperCase());
                return Double.parseDouble(value);
            }
        }
        return null;
    }
}