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BoofCV is an open source Java library for real-time computer vision and robotics applications.
/*
* Copyright (c) 2011-2016, Peter Abeles. All Rights Reserved.
*
* This file is part of BoofCV (http://boofcv.org).
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package boofcv.alg.segmentation.ms;
import boofcv.alg.misc.ImageMiscOps;
import boofcv.struct.ConnectRule;
import boofcv.struct.image.GrayS32;
import georegression.struct.point.Point2D_I32;
import org.ddogleg.struct.GrowQueue_I32;
/**
*
* Given a labeled image in which pixels that contains the same label may or may not be connected to each other,
* create a new labeled image in which only connected pixels have the same label.
* A two pass algorithm is used. In the first pass pixels are examined from top to bottom, left to right. For
* each pixel (the target), the input image and output image labels of its adjacent pixels are examined. If an adjacent
* pixel has the same input label as the target then it is either assigned the same output label or marked for being
* merged. Depending if it is not labeled or has an output label already, respectively. After all the pixels are process
* the merge requests are examined and a new set of output labels is created. A pass across the output image is
* done to relabel the inputs.
*
*
*
* Clustering can be done using 4 or 8 connect, which defines what an adjacent pixel is. 4-connect just considers
* pixels which are (+1,0) (0,1) (-1,0) (0,-1). 8-connect considers (+1,0) (0,1) (-1,0) (0,-1) and
* (1,1) (-1,1) (-1,-1) (1,-1).
*
*
* @author Peter Abeles
*/
public class ClusterLabeledImage extends RegionMergeTree {
// which connectivity rule is used. 4 or 8.
protected ConnectRule connectRule;
// offset in pixel indices for adjacent pixels
protected int edgesIn[];
protected int edgesOut[];
// relative coordinates of adjacent pixels
protected Point2D_I32 edges[];
// contains the number of pixels in each output label
protected GrowQueue_I32 regionMemberCount;
/**
* Configures labeling
*
* @param connectRule Which connectivity rule to use. 4 or 8
*/
public ClusterLabeledImage(ConnectRule connectRule) {
this.connectRule = connectRule;
if( connectRule == ConnectRule.EIGHT ) {
edgesIn = new int[4];
edgesOut = new int[4];
edges = new Point2D_I32[4];
} else if( connectRule == ConnectRule.FOUR ) {
edgesIn = new int[2];
edgesOut = new int[2];
edges = new Point2D_I32[2];
} else {
throw new IllegalArgumentException("connectRule must be 4 or 8");
}
for( int i = 0; i < edges.length; i++ )
edges[i] = new Point2D_I32();
}
/**
* Declares lookup tables for neighbors
*/
protected void setUpEdges(GrayS32 input , GrayS32 output ) {
if( connectRule == ConnectRule.EIGHT ) {
setUpEdges8(input,edgesIn);
setUpEdges8(output,edgesOut);
edges[0].set( 1, 0);
edges[1].set( 1, 1);
edges[2].set( 0, 1);
edges[3].set(-1, 0);
} else {
setUpEdges4(input,edgesIn);
setUpEdges4(output,edgesOut);
edges[0].set( 1,0);
edges[1].set( 0, 1);
}
}
protected void setUpEdges8(GrayS32 image , int edges[] ) {
edges[0] = 1;
edges[1] = 1 + image.stride;
edges[2] = + image.stride;
edges[3] = -1 + image.stride;
}
protected void setUpEdges4(GrayS32 image , int edges[] ) {
edges[0] = 1;
edges[1] = + image.stride;
}
/**
* Relabels the image such that all pixels with the same label are a member of the same graph.
*
* @param input Labeled input image.
* @param output Labeled output image.
* @param regionMemberCount (Input/Output) Number of pixels which belong to each group.
*/
public void process(GrayS32 input , GrayS32 output , GrowQueue_I32 regionMemberCount ) {
// initialize data structures
this.regionMemberCount = regionMemberCount;
regionMemberCount.reset();
setUpEdges(input,output);
ImageMiscOps.fill(output,-1);
// this is a bit of a hack here. Normally you call the parent's init function.
// since the number of regions is not initially known this will grow
mergeList.reset();
connectInner(input, output);
connectLeftRight(input, output);
connectBottom(input, output);
// Merge together all the regions that are connected in the output image
performMerge(output, regionMemberCount);
}
/**
* Examines pixels inside the image without the need for bounds checking
*/
protected void connectInner(GrayS32 input, GrayS32 output) {
int startX = connectRule == ConnectRule.EIGHT ? 1 : 0;
for( int y = 0; y < input.height-1; y++ ) {
int indexIn = input.startIndex + y*input.stride + startX;
int indexOut = output.startIndex + y*output.stride + startX;
for( int x = startX; x < input.width-1; x++ , indexIn++, indexOut++) {
int inputLabel = input.data[indexIn];
int outputLabel = output.data[indexOut];
if( outputLabel == -1 ) { // see if it needs to create a new output segment
output.data[indexOut] = outputLabel = regionMemberCount.size;
regionMemberCount.add(1);
mergeList.add(outputLabel);
}
for( int i = 0; i < edgesIn.length; i++ ) {
if( inputLabel == input.data[indexIn+edgesIn[i]] ) {
int outputAdj = output.data[indexOut+edgesOut[i]];
if( outputAdj == -1 ) { // see if not assigned
regionMemberCount.data[outputLabel]++;
output.data[indexOut+edgesOut[i]] = outputLabel;
} else if( outputLabel != outputAdj ) { // see if assigned to different regions
markMerge(outputLabel,outputAdj);
} // do nothing, same input and output labels
}
}
}
}
}
/**
* Examines pixels along the left and right border
*/
protected void connectLeftRight(GrayS32 input, GrayS32 output) {
for( int y = 0; y < input.height; y++ ) {
int x = input.width-1;
int inputLabel = input.unsafe_get(x, y);
int outputLabel = output.unsafe_get(x, y);
if( outputLabel == -1 ) { // see if it needs to create a new output segment
outputLabel = regionMemberCount.size;
output.unsafe_set(x,y,outputLabel);
regionMemberCount.add(1);
mergeList.add(outputLabel);
}
// check right first
for( int i = 0; i < edges.length; i++ ) {
Point2D_I32 offset = edges[i];
// make sure it is inside the image
if( !input.isInBounds(x+offset.x,y+offset.y))
continue;
if( inputLabel == input.unsafe_get(x+offset.x,y+offset.y) ) {
int outputAdj = output.unsafe_get(x+offset.x,y+offset.y);
if( outputAdj == -1 ) { // see if not assigned
regionMemberCount.data[outputLabel]++;
output.unsafe_set(x+offset.x,y+offset.y, outputLabel);
} else if( outputLabel != outputAdj ) { // see if assigned to different regions
markMerge(outputLabel,outputAdj);
} // do nothing, same input and output labels
}
}
// skip check of left of 4-connect
if( connectRule != ConnectRule.EIGHT )
continue;
x = 0;
inputLabel = input.unsafe_get(x, y);
outputLabel = output.unsafe_get(x, y);
if( outputLabel == -1 ) { // see if it needs to create a new output segment
outputLabel = regionMemberCount.size;
output.unsafe_set(x,y,outputLabel);
regionMemberCount.add(1);
mergeList.add(outputLabel);
}
for( int i = 0; i < edges.length; i++ ) {
Point2D_I32 offset = edges[i];
// make sure it is inside the image
if( !input.isInBounds(x+offset.x,y+offset.y))
continue;
if( inputLabel == input.unsafe_get(x+offset.x,y+offset.y) ) {
int outputAdj = output.unsafe_get(x+offset.x,y+offset.y);
if( outputAdj == -1 ) { // see if not assigned
regionMemberCount.data[outputLabel]++;
output.unsafe_set(x+offset.x,y+offset.y, outputLabel);
} else if( outputLabel != outputAdj ) { // see if assigned to different regions
markMerge(outputLabel,outputAdj);
} // do nothing, same input and output labels
}
}
}
}
/**
* Examines pixels along the bottom border
*/
protected void connectBottom(GrayS32 input, GrayS32 output) {
for( int x = 0; x < input.width-1; x++ ) {
int y = input.height-1;
int inputLabel = input.unsafe_get(x,y);
int outputLabel = output.unsafe_get(x,y);
if( outputLabel == -1 ) { // see if it needs to create a new output segment
outputLabel = regionMemberCount.size;
output.unsafe_set(x,y,outputLabel);
regionMemberCount.add(1);
mergeList.add(outputLabel);
}
// for 4 and 8 connect the check is only +1 x and 0 y
if( inputLabel == input.unsafe_get(x+1,y) ) {
int outputAdj = output.unsafe_get(x+1,y);
if( outputAdj == -1 ) { // see if not assigned
regionMemberCount.data[outputLabel]++;
output.unsafe_set(x+1,y, outputLabel);
} else if( outputLabel != outputAdj ) { // see if assigned to different regions
markMerge(outputLabel,outputAdj);
} // do nothing, same input and output labels
}
}
}
}