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.ImageProcessor;
34
35 /**
36 * An {@link ImageProcessor} that computes the mean of the image's pixels
37 * and subtracts the mean from all pixels.
38 *
39 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
40 */
41 public class MeanCenter implements ImageProcessor<FImage> {
42
43 @Override
44 public void processImage(FImage image) {
45 final int width = image.width;
46 final int height = image.height;
47 final float[][] data = image.pixels;
48
49 image.subtractInplace(patchMean(data, 0, 0, width, height));
50 }
51
52 /**
53 * same as {@link #patchMean(float[][], int, int, int, int)} but the width and height are taken from data[0].length and data.length
54 * @param data
55 * @return the patch mean
56 */
57 public static final float patchMean(final float[][] data){
58 return patchMean(data, 0, 0, data.length > 0 && data[0]!=null ? data[0].length : 0, data.length);
59 }
60 /**
61 * Finds the mean value of a sub-patch of a 2D float array.
62 * @param data the array
63 * @param x the location of the sub-patch
64 * @param y the location of the sub-patch
65 * @param width sub-patch width
66 * @param height sub-patch height
67 * @return the mean value
68 */
69 public static final float patchMean(final float[][] data, final int x, final int y, final int width, final int height) {
70 float accum = 0;
71
72 final int endX = width + x;
73 final int endY = height + y;
74
75 for (int yy=y; yy<endY; yy++) {
76 for (int xx=x; xx<endX; xx++) {
77 accum += data[yy][xx];
78 }
79 }
80
81 float mean = accum / (float)(width * height);
82 return mean;
83 }
84 }