algorithms.quality.JndRegionSize.java Source code

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Here is the source code for algorithms.quality.JndRegionSize.java

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/*
 * Copyright 2014 Fraunhofer IGD
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package algorithms.quality;

import java.awt.geom.Point2D;
import java.util.List;

import org.apache.commons.math3.stat.descriptive.DescriptiveStatistics;

import algorithms.JndRegionComputer;
import algorithms.sampling.SamplingStrategy;
import colormaps.Colormap2D;

/**
 * Computes the variance in jnd region size
 * @author Martin Steiger
 */
public class JndRegionSize implements ColormapQuality {
    private final SamplingStrategy sampling;

    /**
     * @param sampling the sampling to use
     */
    public JndRegionSize(SamplingStrategy sampling) {
        this.sampling = sampling;
    }

    @Override
    public double getQuality(Colormap2D colormap) {
        JndRegionComputer computer = new JndRegionComputer(colormap, sampling, 3.0);

        DescriptiveStatistics stats = new DescriptiveStatistics();

        for (Point2D center : computer.getPoints()) {
            List<Point2D> poly = computer.getRegion(center);
            double area = computeArea(poly, center);

            stats.addValue(area);
        }

        // TODO: find a better scaling factor
        return stats.getVariance() * 10000000.d;
    }

    private double computeArea(List<Point2D> poly, Point2D center) {
        double sum = 0;
        for (int i = 0; i < poly.size(); i++) {
            Point2D p0 = poly.get(i);
            Point2D p1 = poly.get((i + 1) % poly.size());

            sum = sum + p0.getX() * p1.getY() - p0.getY() * p1.getX();
        }

        double area = Math.abs(sum / 2);
        return area;
    }

    @Override
    public String getName() {
        return "Region Size";
    }

    @Override
    public String getDescription() {
        return "Compute the jnd regions values based on a sampling strategy and returns the variance of the jnd region size across the colormap";
    }
}