001/**
002 * Copyright (c) 2011, The University of Southampton and the individual contributors.
003 * All rights reserved.
004 *
005 * Redistribution and use in source and binary forms, with or without modification,
006 * are permitted provided that the following conditions are met:
007 *
008 *   *  Redistributions of source code must retain the above copyright notice,
009 *      this list of conditions and the following disclaimer.
010 *
011 *   *  Redistributions in binary form must reproduce the above copyright notice,
012 *      this list of conditions and the following disclaimer in the documentation
013 *      and/or other materials provided with the distribution.
014 *
015 *   *  Neither the name of the University of Southampton nor the names of its
016 *      contributors may be used to endorse or promote products derived from this
017 *      software without specific prior written permission.
018 *
019 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
020 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
021 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
022 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
023 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
024 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
025 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
026 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
027 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
028 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029 */
030package org.openimaj.image.processing.algorithm;
031
032import org.openimaj.image.FImage;
033import org.openimaj.image.processor.SinglebandImageProcessor;
034
035import edu.emory.mathcs.jtransforms.fft.FloatFFT_2D;
036
037/**
038 * {@link FImage} correlation performed using an FFT.
039 * 
040 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
041 *
042 */
043public class FourierCorrelation implements SinglebandImageProcessor<Float, FImage> {
044        /**
045         * The template image
046         */
047        public FImage template;
048        
049        /**
050         * Construct the correlation operator with the given template
051         * @param template the template
052         */
053        public FourierCorrelation(FImage template) {
054                this.template = template;
055        }
056        
057        @Override
058        public void processImage(FImage image) {
059                correlate(image, template, true);
060        }
061
062        /**
063         * Correlate an image with a kernel using an FFT.
064         * @param image The image 
065         * @param template The template to correlate with the image
066         * @param inplace if true, then output overwrites the input, otherwise a new image is created.
067         * @return correlation map
068         */
069        public static FImage correlate(FImage image, FImage template, boolean inplace) {
070                final int cols = image.getCols();
071                final int rows = image.getRows();
072
073                FloatFFT_2D fft = new FloatFFT_2D(rows, cols);
074
075                float[][] preparedImage = FourierTransform.prepareData(image.pixels, rows, cols, false);
076                fft.complexForward(preparedImage);
077
078                float[][] preparedKernel = FourierTransform.prepareData(template.pixels, rows, cols, false);
079                fft.complexForward(preparedKernel);
080
081                for(int y = 0; y < rows; y++) {
082                        for(int x = 0; x < cols; x++) {
083                                float reImage = preparedImage[y][x*2];
084                                float imImage = preparedImage[y][1 + x*2];
085
086                                float reKernel = preparedKernel[y][x*2];
087                                float imKernelConj = -1 * preparedKernel[y][1 + x*2];
088
089                                float re = reImage * reKernel - imImage * imKernelConj;
090                                float im = reImage * imKernelConj + imImage * reKernel;
091
092                                preparedImage[y][x*2] = re;
093                                preparedImage[y][1 + x*2] = im;
094                        }
095                }
096
097                fft.complexInverse(preparedImage, true);
098
099                FImage out = image;
100                if (!inplace) 
101                        out = new FImage(cols, rows);
102
103                FourierTransform.unprepareData(preparedImage, out, false);
104                
105                return out;
106        }
107}