1 /**
2 * Copyright (c) 2011, The University of Southampton and the individual contributors.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without modification,
6 * are permitted provided that the following conditions are met:
7 *
8 * * Redistributions of source code must retain the above copyright notice,
9 * this list of conditions and the following disclaimer.
10 *
11 * * Redistributions in binary form must reproduce the above copyright notice,
12 * this list of conditions and the following disclaimer in the documentation
13 * and/or other materials provided with the distribution.
14 *
15 * * Neither the name of the University of Southampton nor the names of its
16 * contributors may be used to endorse or promote products derived from this
17 * software without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
21 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
22 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
23 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
24 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
25 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
26 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
28 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30 package org.openimaj.image.processing.algorithm;
31
32 import org.openimaj.image.FImage;
33 import org.openimaj.image.processor.SinglebandImageProcessor;
34
35 import edu.emory.mathcs.jtransforms.fft.FloatFFT_2D;
36
37 /**
38 * {@link FImage} correlation performed using an FFT.
39 *
40 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
41 *
42 */
43 public class FourierCorrelation implements SinglebandImageProcessor<Float, FImage> {
44 /**
45 * The template image
46 */
47 public FImage template;
48
49 /**
50 * Construct the correlation operator with the given template
51 * @param template the template
52 */
53 public FourierCorrelation(FImage template) {
54 this.template = template;
55 }
56
57 @Override
58 public void processImage(FImage image) {
59 correlate(image, template, true);
60 }
61
62 /**
63 * Correlate an image with a kernel using an FFT.
64 * @param image The image
65 * @param template The template to correlate with the image
66 * @param inplace if true, then output overwrites the input, otherwise a new image is created.
67 * @return correlation map
68 */
69 public static FImage correlate(FImage image, FImage template, boolean inplace) {
70 final int cols = image.getCols();
71 final int rows = image.getRows();
72
73 FloatFFT_2D fft = new FloatFFT_2D(rows, cols);
74
75 float[][] preparedImage = FourierTransform.prepareData(image.pixels, rows, cols, false);
76 fft.complexForward(preparedImage);
77
78 float[][] preparedKernel = FourierTransform.prepareData(template.pixels, rows, cols, false);
79 fft.complexForward(preparedKernel);
80
81 for(int y = 0; y < rows; y++) {
82 for(int x = 0; x < cols; x++) {
83 float reImage = preparedImage[y][x*2];
84 float imImage = preparedImage[y][1 + x*2];
85
86 float reKernel = preparedKernel[y][x*2];
87 float imKernelConj = -1 * preparedKernel[y][1 + x*2];
88
89 float re = reImage * reKernel - imImage * imKernelConj;
90 float im = reImage * imKernelConj + imImage * reKernel;
91
92 preparedImage[y][x*2] = re;
93 preparedImage[y][1 + x*2] = im;
94 }
95 }
96
97 fft.complexInverse(preparedImage, true);
98
99 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 }