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.convolution;
031
032import org.openimaj.image.FImage;
033import org.openimaj.image.processor.SinglebandKernelProcessor;
034
035/**
036 * Apply the sobel operator to an image. This is achieved using a kernel convolution in the X and Y. 
037 * The kernels are normalised 3x3 first derivatives of a gaussian of sigma 1.0f
038 * 
039 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
040 * @author Sina Samangooei (ss@ecs.soton.ac.uk)
041 *
042 */
043public class FSobelMagnitude implements SinglebandKernelProcessor<Float, FImage> {
044
045        /**
046         * The 3x3 derivative of a gaussian of sigma 1 in the x direction
047         */
048        public static final FImage KERNEL_X = new FImage(new float[][] {
049                        {1,0,-1},
050                        {2,0,-2},
051                        {1,0,-1}        
052        });
053
054        /**
055         * The 3x3 derivative of a gaussian of sigma 1 in the x direction
056         */
057        public static final FImage KERNEL_Y = new FImage(new float[][] {
058                        { 1, 2, 1},
059                        { 0, 0, 0},
060                        {-1,-2,-1}
061        });
062
063        @Override
064        public int getKernelHeight() {
065                return 3;
066        }
067
068        @Override
069        public int getKernelWidth() {
070                return 3;
071        }
072
073        @Override
074        public Float processKernel(FImage patch) {
075                float sumx=0, sumy=0;
076
077                for (int r=0; r<3; r++) {
078                        for (int c=0; c<3; c++) {
079                                sumx += (KERNEL_X.pixels[2-r][2-c] * patch.pixels[r][c]);
080                                sumy += (KERNEL_Y.pixels[2-r][2-c] * patch.pixels[r][c]);
081                        }
082                }
083
084                return (float)Math.sqrt((sumx*sumx) + (sumy*sumy));
085        }       
086}