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OptaPlanner solves planning problems. This lightweight, embeddable planning engine implements powerful and scalable algorithms to optimize business resource scheduling and planning. This module contains the examples which demonstrate how to use it in a normal Java application.
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package org.optaplanner.examples.tsp.persistence;

import java.io.IOException;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.List;

import org.optaplanner.examples.common.business.SolutionBusiness;
import org.optaplanner.examples.common.persistence.AbstractPngSolutionImporter;
import org.optaplanner.examples.common.persistence.SolutionConverter;
import org.optaplanner.examples.tsp.app.TspApp;
import org.optaplanner.examples.tsp.domain.Domicile;
import org.optaplanner.examples.tsp.domain.TspSolution;
import org.optaplanner.examples.tsp.domain.Visit;
import org.optaplanner.examples.tsp.domain.location.AirLocation;
import org.optaplanner.examples.tsp.domain.location.DistanceType;
import org.optaplanner.examples.tsp.domain.location.Location;

public class TspImageStipplerImporter extends AbstractPngSolutionImporter {

    private static final double GRAY_MAXIMUM = 256.0 * 3.0;

    public static void main(String[] args) {
        SolutionConverter converter = SolutionConverter.createImportConverter(TspApp.DATA_DIR_NAME,
                new TspImageStipplerImporter(), new TspSolutionFileIO());
        converter.convertAll();
    }

    @Override
    public PngInputBuilder createPngInputBuilder() {
        return new TspImageStipplerInputBuilder();
    }

    public static class TspImageStipplerInputBuilder extends PngInputBuilder {

        private TspSolution tspSolution;

        private int locationListSize;

        @Override
        public TspSolution readSolution() throws IOException {
            tspSolution = new TspSolution(0L);
            tspSolution.setName(SolutionBusiness.getBaseFileName(inputFile));
            floydSteinbergDithering();
            createVisitList();
            BigInteger possibleSolutionSize = factorial(tspSolution.getLocationList().size() - 1);
            logger.info("TspSolution {} has {} locations with a search space of {}.",
                    getInputId(),
                    tspSolution.getLocationList().size(),
                    getFlooredPossibleSolutionSize(possibleSolutionSize));
            return tspSolution;
        }

        /**
         * As described by Floyd-Steinberg
         * dithering.
         */
        private void floydSteinbergDithering() {
            tspSolution.setDistanceType(DistanceType.AIR_DISTANCE);
            tspSolution.setDistanceUnitOfMeasurement("distance");
            int width = image.getWidth();
            int height = image.getHeight();
            double[][] errorDiffusion = new double[width][height];
            List locationList = new ArrayList<>(1000);
            long id = 0L;
            for (int y = 0; y < height; y++) {
                for (int x = 0; x < width; x++) {
                    int rgb = image.getRGB(x, y);
                    int r = (rgb) & 0xFF;
                    int g = (rgb >> 8) & 0xFF;
                    int b = (rgb >> 16) & 0xFF;
                    double originalGray = (r + g + b) / GRAY_MAXIMUM;
                    double diffusedGray = originalGray + errorDiffusion[x][y];
                    double error;
                    if (diffusedGray <= 0.5) {
                        Location location = new AirLocation(id, -y, x);
                        id++;
                        locationList.add(location);
                        error = diffusedGray;
                    } else {
                        error = diffusedGray - 1.0;
                    }
                    if (x + 1 < width) {
                        errorDiffusion[x + 1][y] += error * 7.0 / 16.0;
                    }
                    if (y + 1 < height) {
                        if (x - 1 >= 0) {
                            errorDiffusion[x - 1][y + 1] += error * 3.0 / 16.0;
                        }
                        errorDiffusion[x][y + 1] += error * 5.0 / 16.0;
                        if (x + 1 < width) {
                            errorDiffusion[x + 1][y + 1] += error * 1.0 / 16.0;
                        }
                    }
                }
            }
            tspSolution.setLocationList(locationList);
        }

        private void createVisitList() {
            List locationList = tspSolution.getLocationList();
            List visitList = new ArrayList<>(locationList.size() - 1);
            int count = 0;
            for (Location location : locationList) {
                if (count < 1) {
                    Domicile domicile = new Domicile(location.getId(), location);
                    tspSolution.setDomicile(domicile);
                } else {
                    Visit visit = new Visit(location.getId(), location);
                    // Notice that we leave the PlanningVariable properties on null
                    visitList.add(visit);
                }
                count++;
            }
            tspSolution.setVisitList(visitList);
        }

    }

}