/**
 * Copyright (c) 2011, The University of Southampton and the individual contributors.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 *   *  Redistributions of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 *
 *   *  Redistributions in binary form must reproduce the above copyright notice,
 *      this list of conditions and the following disclaimer in the documentation
 *      and/or other materials provided with the distribution.
 *
 *   *  Neither the name of the University of Southampton nor the names of its
 *      contributors may be used to endorse or promote products derived from this
 *      software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
/**
 *
 */
package org.openimaj.image.processing.face.tracking;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.openimaj.image.FImage;
import org.openimaj.image.processing.face.detection.DetectedFace;
import org.openimaj.image.processing.face.detection.HaarCascadeDetector;
import org.openimaj.math.geometry.shape.Rectangle;
import org.openimaj.video.processing.tracking.BasicObjectTracker;
import org.openimaj.video.tracking.klt.KLTTracker;

/**
 * A face tracker that uses the {@link HaarCascadeDetector} to detect faces in
 * the image and then tracks them using the {@link KLTTracker}.
 *
 * @author David Dupplaw (dpd@ecs.soton.ac.uk)
 *
 * @created 13 Oct 2011
 */
public class KLTHaarFaceTracker implements FaceTracker<FImage> {
        /** The face detector used to detect the faces */
        private final HaarCascadeDetector faceDetector = new HaarCascadeDetector();

        /** A list of trackers that are tracking faces within the image */
        private final List<BasicObjectTracker> trackers = new ArrayList<BasicObjectTracker>();

        /** The previous frame */
        private FImage previousFrame = null;

        /** When all faces are lost, the frame is retried */
        private boolean retryFrame = false;

        /** The number of frames to force a retry */
        private int forceRetry = -1;

        /** Used for forcing retry */
        private int frameCounter = 0;

        private final float detectionScalar = 1.2f;

        /**
         * Default constructor that takes the minimum size (in pixels) of detections
         * that should be considered faces.
         *
         * @param minSize
         *            The minimum size of face boxes
         */
        public KLTHaarFaceTracker(final int minSize) {
                this.faceDetector.setMinSize(minSize);
        }

        /**
         * Used to detect faces when there is no current state.
         *
         * @return The list of detected faces
         */
        private List<DetectedFace> detectFaces(final FImage img) {
                return this.faceDetector.detectFaces(img);
        }

        /**
         * {@inheritDoc}
         *
         * @see org.openimaj.image.processing.face.tracking.FaceTracker#trackFace(org.openimaj.image.Image)
         */
        @Override
        public List<DetectedFace> trackFace(final FImage img)
        {
                List<DetectedFace> detectedFaces = new ArrayList<DetectedFace>();

                // Determine whether we need to force a retry now
                if (this.forceRetry != -1 && this.frameCounter % this.forceRetry == 0)
                        this.trackers.clear();

                // If we're just starting tracking, find some features and start
                // tracking them.
                if (this.previousFrame == null || this.trackers.size() == 0) {

                        // Detect the faces in the image.
                        final List<DetectedFace> faces = this.detectFaces(img);

                        // Create trackers for each face found
                        for (final DetectedFace face : faces) {
                                // Create a new tracker for this face
                                final BasicObjectTracker faceTracker = new BasicObjectTracker();
                                final Rectangle r = face.getBounds();
                                r.scaleCentroid(this.detectionScalar);
                                faceTracker.initialiseTracking(r, img);
                                this.trackers.add(faceTracker);

                                // Store the last frame
                                this.previousFrame = img;
                        }

                        detectedFaces = faces;
                } else
                        // If we have a previous frame, attempt to track the frame
                        if (this.previousFrame != null) {
                                // Update all the trackers
                                final Iterator<BasicObjectTracker> i = this.trackers.iterator();
                                while (i.hasNext()) {
                                        final BasicObjectTracker tracker = i.next();
                                        if (tracker.trackObject(img).size() == 0)
                                                i.remove();
                                        else {
                                                // Store the bounding box of the tracked features as the
                                                // face
                                                detectedFaces
                                                .add(new DetectedFace(
                                                                tracker.getFeatureList().getBounds(),
                                                                img.extractROI(tracker.getFeatureList().getBounds()),
                                                                tracker.getFeatureList().countRemainingFeatures()));

                                                // Store the last frame
                                                this.previousFrame = img;
                                        }
                                }

                                if (this.trackers.size() == 0 && this.retryFrame == false) {
                                        this.retryFrame = true;
                                        detectedFaces = this.trackFace(img);
                                }
                        }

                this.frameCounter++;
                this.retryFrame = false;
                return detectedFaces;
        }

        /**
         * @return the forceRetry
         */
        public int getForceRetry()
        {
                return this.forceRetry;
        }

        /**
         * @param forceRetry
         *            the forceRetry to set
         */
        public void setForceRetry(final int forceRetry)
        {
                this.forceRetry = forceRetry;
        }
}