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.connectedcomponent; 31 32 import java.util.ArrayList; 33 import java.util.LinkedHashSet; 34 import java.util.List; 35 36 import org.openimaj.image.FImage; 37 import org.openimaj.image.analyser.ImageAnalyser; 38 import org.openimaj.image.pixel.ConnectedComponent; 39 import org.openimaj.image.pixel.Pixel; 40 41 /** 42 * A Connected Component Labeler for grey-level images. This class can be used 43 * to transform an image that represents a map of labeled objects into a list of 44 * {@link ConnectedComponent}s. 45 * <p> 46 * Internally we use a flood-fill approach to finding the 47 * {@link ConnectedComponent}s. 48 * 49 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk) 50 */ 51 public class GreyscaleConnectedComponentLabeler implements ImageAnalyser<FImage> { 52 List<ConnectedComponent> components; 53 54 /** 55 * Syntactic sugar for calling {@link #analyseImage(FImage)} followed by 56 * {@link #getComponents()}; 57 * 58 * @param image 59 * the image to extract components from 60 * @return the extracted components. 61 */ 62 public List<ConnectedComponent> findComponents(FImage image) { 63 analyseImage(image); 64 return components; 65 } 66 67 protected ConnectedComponent floodFill(FImage image, Pixel start, int[][] output, int color) { 68 final ConnectedComponent cc = new ConnectedComponent(); 69 // Flood-fill (node, target-color, replacement-color): 70 // 1. Set Q to the empty queue. 71 // Queue<Pixel> queue = new LinkedList<Pixel>(); 72 final LinkedHashSet<Pixel> queue = new LinkedHashSet<Pixel>(); 73 74 // 2. If the color of node is not equal to target-color, return. 75 final float targetColour = image.pixels[start.y][start.x]; 76 77 // 3. Add node to Q. 78 queue.add(start); 79 // 4. For each element n of Q: 80 while (queue.size() > 0) { 81 // Pixel n = queue.poll(); 82 final Pixel n = queue.iterator().next(); 83 queue.remove(n); 84 85 // 5. If the color of n is equal to target-color: 86 if (image.pixels[n.y][n.x] == targetColour && output[n.y][n.x] != color) { 87 // 6. Set w and e equal to n. 88 int e = n.x, w = n.x; 89 // 7. Move w to the west until the color of the node to the west 90 // of w no longer matches target-color. 91 while (w > 0 && image.pixels[n.y][w - 1] == targetColour) 92 w--; 93 94 // 8. Move e to the east until the color of the node to the east 95 // of e no longer matches target-color. 96 while (e < image.width - 1 && image.pixels[n.y][e + 1] == targetColour) 97 e++; 98 99 // 9. Set the color of nodes between w and e to 100 // replacement-color. 101 for (int i = w; i <= e; i++) { 102 output[n.y][i] = color; 103 cc.addPixel(i, n.y); 104 105 // 10. For each node n between w and e: 106 final int north = n.y - 1; 107 final int south = n.y + 1; 108 // 11. If the color of the node to the north of n is 109 // target-color, add that node to Q. 110 if (north >= 0 && image.pixels[north][i] == targetColour && output[north][i] != color) 111 queue.add(new Pixel(i, north)); 112 // If the color of the node to the south of n is 113 // target-color, add that node to Q. 114 if (south < image.height && image.pixels[south][i] == targetColour && output[south][i] != color) 115 queue.add(new Pixel(i, south)); 116 } 117 // 12. Continue looping until Q is exhausted. 118 } 119 } 120 // 13. Return. 121 return cc; 122 } 123 124 @Override 125 public void analyseImage(FImage image) { 126 components = new ArrayList<ConnectedComponent>(); 127 128 final int[][] labels = new int[image.height][image.width]; 129 int nextColor = 1; 130 131 for (int y = 0; y < image.height; y++) { 132 for (int x = 0; x < image.width; x++) { 133 if (labels[y][x] == 0) { 134 components.add(floodFill(image, new Pixel(x, y), labels, nextColor)); 135 nextColor++; 136 } 137 } 138 } 139 } 140 141 /** 142 * @return the list of components found in the last call to 143 * {@link #analyseImage(FImage)}. 144 */ 145 public List<ConnectedComponent> getComponents() { 146 return components; 147 } 148 }