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.SinglebandImageProcessor; 034 035/** 036 * Image processor for separable convolution of an FImage. Capable of doing 037 * convolution in either the vertical, horizontal or both directions. 038 * 039 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk) 040 */ 041public class FImageConvolveSeparable implements SinglebandImageProcessor<Float, FImage> { 042 float[] hkernel; 043 float[] vkernel; 044 045 /** 046 * Specify the horizontal kernel and vertical kernel separately. 047 * 048 * @param hkernel 049 * horizontal kernel 050 * @param vkernel 051 * vertical kernel 052 */ 053 public FImageConvolveSeparable(float[] hkernel, float[] vkernel) { 054 this.hkernel = hkernel; 055 this.vkernel = vkernel; 056 } 057 058 /** 059 * Specify a single kernel to be used as the horizontal and vertical. 060 * 061 * @param kernel 062 * both kernels 063 */ 064 public FImageConvolveSeparable(float[] kernel) { 065 this.hkernel = kernel; 066 this.vkernel = kernel; 067 } 068 069 /* 070 * (non-Javadoc) 071 * 072 * @see 073 * org.openimaj.image.processor.ImageProcessor#processImage(org.openimaj 074 * .image.Image) 075 */ 076 @Override 077 public void processImage(FImage image) { 078 if (hkernel != null) 079 convolveHorizontal(image, hkernel); 080 if (vkernel != null) 081 convolveVertical(image, vkernel); 082 } 083 084 /* 085 * Convolve an array of data with a kernel. The data must be padded at each 086 * end by half the kernel width (with replicated data or zeros). The output 087 * is written back into the data buffer, starting at the beginning and is 088 * valid through buffer.length-kernel.length. 089 */ 090 protected static void convolveBuffer(float[] buffer, float[] kernel) 091 { 092 final int l = buffer.length - kernel.length; 093 for (int i = 0; i < l; i++) { 094 float sum = 0.0f; 095 096 for (int j = 0, jj = kernel.length - 1; j < kernel.length; j++, jj--) 097 sum += buffer[i + j] * kernel[jj]; 098 099 buffer[i] = sum; 100 } 101 } 102 103 /** 104 * Convolve the image in the horizontal direction with the kernel. Edge 105 * effects are handled by duplicating the edge pixels. 106 * 107 * @param image 108 * the image to convolve. 109 * @param kernel 110 * the convolution kernel. 111 */ 112 public static void convolveHorizontal(FImage image, float[] kernel) { 113 final int halfsize = kernel.length / 2; 114 115 final float buffer[] = new float[image.width + kernel.length]; 116 117 for (int r = 0; r < image.height; r++) { 118 for (int i = 0; i < halfsize; i++) 119 buffer[i] = image.pixels[r][0]; 120 for (int i = 0; i < image.width; i++) 121 buffer[halfsize + i] = image.pixels[r][i]; 122 for (int i = 0; i < halfsize; i++) 123 buffer[halfsize + image.width + i] = image.pixels[r][image.width - 1]; 124 125 // convolveBuffer(buffer, kernel); 126 final int l = buffer.length - kernel.length; 127 for (int i = 0; i < l; i++) { 128 float sum = 0.0f; 129 130 for (int j = 0, jj = kernel.length - 1; j < kernel.length; j++, jj--) 131 sum += buffer[i + j] * kernel[jj]; 132 133 buffer[i] = sum; 134 } 135 // end convolveBuffer(buffer, kernel); 136 137 for (int c = 0; c < image.width; c++) 138 image.pixels[r][c] = buffer[c]; 139 } 140 } 141 142 /** 143 * Convolve the image in the vertical direction with the kernel. Edge 144 * effects are handled by duplicating the edge pixels. 145 * 146 * @param image 147 * the image to convolve. 148 * @param kernel 149 * the convolution kernel. 150 */ 151 public static void convolveVertical(FImage image, float[] kernel) { 152 final int halfsize = kernel.length / 2; 153 154 final float buffer[] = new float[image.height + kernel.length]; 155 156 for (int c = 0; c < image.width; c++) { 157 for (int i = 0; i < halfsize; i++) 158 buffer[i] = image.pixels[0][c]; 159 for (int i = 0; i < image.height; i++) 160 buffer[halfsize + i] = image.pixels[i][c]; 161 for (int i = 0; i < halfsize; i++) 162 buffer[halfsize + image.height + i] = image.pixels[image.height - 1][c]; 163 164 // convolveBuffer(buffer, kernel); 165 final int l = buffer.length - kernel.length; 166 for (int i = 0; i < l; i++) { 167 float sum = 0.0f; 168 169 for (int j = 0, jj = kernel.length - 1; j < kernel.length; j++, jj--) 170 sum += buffer[i + j] * kernel[jj]; 171 172 buffer[i] = sum; 173 } 174 // end convolveBuffer(buffer, kernel); 175 176 for (int r = 0; r < image.height; r++) 177 image.pixels[r][c] = buffer[r]; 178 } 179 } 180 181 /** 182 * Fast convolution for separated 3x3 kernels. Only valid pixels are 183 * considered, so the output image bounds will be two pixels smaller than 184 * the input image on all sides (the response of the kernel to the source 185 * pixel at 1,1 is stored in the destination image at 0,0) 186 * 187 * @param source 188 * the source image 189 * @param dest 190 * the destination image 191 * @param kx 192 * the x-kernel (can be null, implying [0 1 0] ) 193 * @param ky 194 * the y-kernel (can be null, implying [0 1 0]) 195 * @param buffer 196 * the working buffer (can be null, but ideally the same width as 197 * the source image) 198 */ 199 public static void fastConvolve3(FImage source, FImage dest, float[] kx, float[] ky, float[] buffer) 200 { 201 final int dst_width = source.width - 2; 202 203 if (kx == null) 204 kx = new float[] { 0, 1, 0 }; 205 if (ky == null) 206 ky = new float[] { 0, 1, 0 }; 207 208 if (buffer == null || buffer.length < source.width) 209 buffer = new float[source.width]; 210 211 for (int y = 0; y <= source.height - 3; y++) { 212 final float[] src = source.pixels[y]; 213 final float[] src2 = source.pixels[y + 1]; 214 final float[] src3 = source.pixels[y + 2]; 215 216 for (int x = 0; x < source.width; x++) 217 { 218 buffer[x] = ky[0] * src[x] + ky[1] * src2[x] + ky[2] * src3[x]; 219 } 220 221 for (int x = 0; x < dst_width; x++) 222 { 223 dest.pixels[y][x] = kx[0] * buffer[x] + kx[1] * buffer[x + 1] + kx[2] * buffer[x + 2]; 224 } 225 } 226 } 227}