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.processor.PixelProcessor;
33
34 /**
35 * Class to perform Gamma correction on a grey-level image.
36 * Grey levels are transformed such that I_new = I^Gamma for
37 * Gamma > 0 and all pixels I. If Gamma == 0 then the transform
38 * is I_new = log(I).
39 *
40 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
41 *
42 */
43 public class GammaCorrection implements PixelProcessor<Float> {
44 protected double gamma;
45
46 /**
47 * Construct a GammaCorrection with the default gamma of 0.2
48 */
49 public GammaCorrection() {
50 this.gamma = 0.2;
51 }
52
53 /**
54 * Construct a GammaCorrection with the given gamma
55 * @param gamma The gamma value to use
56 */
57 public GammaCorrection(double gamma) {
58 this.gamma = gamma;
59 }
60
61 @Override
62 public Float processPixel(Float pixel) {
63 if (gamma == 0) {
64 return (float) Math.log(pixel);
65 }
66 return (float) Math.pow(pixel, gamma);
67 }
68 }
69