/*
* 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.segmentation.ComputeRegionMeanColor;
import boofcv.struct.ConnectRule;
import boofcv.struct.image.GrayS32;
import boofcv.struct.image.ImageBase;
import georegression.struct.point.Point2D_I32;
import org.ddogleg.struct.FastQueue;
import org.ddogleg.struct.GrowQueue_B;
import org.ddogleg.struct.GrowQueue_I32;
/**
* Finds regions which are too small and merges them with a neighbor that is the most similar to it and connected.
* The process is repeated until there are no more regions below the size threshold. How similar two neighbors are
* is determined using each region's average color. Connectivity is determined using a 4-connect rule.
*
* @author Peter Abeles
*/
public class MergeSmallRegions<T extends ImageBase> extends RegionMergeTree {
// minimum allowed size of a region, inclusive
protected int minimumSize;
// Computes the color of each region
protected ComputeRegionMeanColor<T> computeColor;
// List which indicates ia segment is to be pruned based on its ID
protected GrowQueue_B segmentPruneFlag = new GrowQueue_B();
// Conversion between segment ID and prune ID
protected GrowQueue_I32 segmentToPruneID = new GrowQueue_I32();
// Used to mark pixels as not being a member of any region
protected FastQueue<Node> pruneGraph = new FastQueue<>(Node.class, true);
// Relative location of neighbors according to connection rule
protected Point2D_I32 connect[];
/**
* Constructor
*
* @param minimumSize Minimum number of pixels a region must have for it to not be pruned.
* @param computeColor Computes the color of each region
*/
public MergeSmallRegions(int minimumSize, ConnectRule rule , ComputeRegionMeanColor<T> computeColor) {
this.minimumSize = minimumSize;
this.computeColor = computeColor;
if( rule == ConnectRule.FOUR ) {
connect = new Point2D_I32[4];
connect[0] = new Point2D_I32(1,0);
connect[1] = new Point2D_I32(0,1);
connect[2] = new Point2D_I32(-1,0);
connect[3] = new Point2D_I32(0,-1);
} else if( rule == ConnectRule.EIGHT ) {
connect = new Point2D_I32[8];
connect[0] = new Point2D_I32(1,0);
connect[1] = new Point2D_I32(0,1);
connect[2] = new Point2D_I32(-1,0);
connect[3] = new Point2D_I32(0,-1);
connect[4] = new Point2D_I32( 1, 1);
connect[5] = new Point2D_I32(-1, 1);
connect[6] = new Point2D_I32(-1,-1);
connect[7] = new Point2D_I32( 1,-1);
} else {
throw new IllegalArgumentException("Unknown connect rule "+rule);
}
}
public void setMinimumSize(int minimumSize) {
this.minimumSize = minimumSize;
}
/**
* Merges together smaller regions. Segmented image, region member count, and region color are all updated.
*
* @param image Input image. Used to compute color of each region
* @param pixelToRegion (input/output) Segmented image with the ID of each region. Modified.
* @param regionMemberCount (input/output) Number of members in each region Modified.
* @param regionColor (Output) Storage for colors of each region. Will contains the color of each region on output.
*/
public void process( T image,
GrayS32 pixelToRegion ,
GrowQueue_I32 regionMemberCount,
FastQueue<float[]> regionColor ) {
// iterate until no more regions need to be merged together
while( true ) {
// Update the color of each region
regionColor.resize(regionMemberCount.size);
computeColor.process(image, pixelToRegion, regionMemberCount, regionColor);
initializeMerge(regionMemberCount.size);
// Create a list of regions which are to be pruned
if( !setupPruneList(regionMemberCount) )
break;
// Scan the image and create a list of regions which the pruned regions connect to
findAdjacentRegions(pixelToRegion);
// Select the closest match to merge into
for( int i = 0; i < pruneGraph.size; i++ ) {
selectMerge(i,regionColor);
}
// Do the usual merge stuff
performMerge(pixelToRegion,regionMemberCount);
}
}
/**
* Identifies which regions are to be pruned based on their member counts. Then sets up
* data structures for graph and converting segment ID to prune ID.
*
* @return true If elements need to be pruned and false if not.
*/
protected boolean setupPruneList(GrowQueue_I32 regionMemberCount) {
segmentPruneFlag.resize(regionMemberCount.size);
pruneGraph.reset();
segmentToPruneID.resize(regionMemberCount.size);
for( int i = 0; i < regionMemberCount.size; i++ ) {
if( regionMemberCount.get(i) < minimumSize ) {
segmentToPruneID.set(i, pruneGraph.size());
Node n = pruneGraph.grow();
n.init(i);
segmentPruneFlag.set(i, true);
} else {
segmentPruneFlag.set(i, false);
}
}
return pruneGraph.size() != 0;
}
/**
* Go through each pixel in the image and examine its neighbors according to a 4-connect rule. If one of
* the pixels is in a region that is to be pruned mark them as neighbors. The image is traversed such that
* the number of comparisons is minimized.
*/
protected void findAdjacentRegions(GrayS32 pixelToRegion) {
// -------- Do the inner pixels first
if( connect.length == 4 )
adjacentInner4(pixelToRegion);
else if( connect.length == 8 ) {
adjacentInner8(pixelToRegion);
}
adjacentBorder(pixelToRegion);
}
protected void adjacentInner4(GrayS32 pixelToRegion) {
for( int y = 0; y < pixelToRegion.height-1; y++ ) {
int indexImg = pixelToRegion.startIndex + pixelToRegion.stride*y;
for( int x = 0; x < pixelToRegion.width-1; x++ , indexImg++ ) {
int regionA = pixelToRegion.data[indexImg];
// x + 1 , y
int regionB = pixelToRegion.data[indexImg+1];
// x , y + 1
int regionC = pixelToRegion.data[indexImg+pixelToRegion.stride];
boolean pruneA = segmentPruneFlag.data[regionA];
if( regionA != regionB ) {
boolean pruneB = segmentPruneFlag.data[regionB];
if( pruneA ) {
Node n = pruneGraph.get(segmentToPruneID.get(regionA));
n.connect(regionB);
}
if( pruneB ) {
Node n = pruneGraph.get(segmentToPruneID.get(regionB));
n.connect(regionA);
}
}
if( regionA != regionC ) {
boolean pruneC = segmentPruneFlag.data[regionC];
if( pruneA ) {
Node n = pruneGraph.get(segmentToPruneID.get(regionA));
n.connect(regionC);
}
if( pruneC ) {
Node n = pruneGraph.get(segmentToPruneID.get(regionC));
n.connect(regionA);
}
}
}
}
}
protected void adjacentInner8(GrayS32 pixelToRegion) {
for( int y = 0; y < pixelToRegion.height-1; y++ ) {
int indexImg = pixelToRegion.startIndex + pixelToRegion.stride*y+1;
for( int x = 1; x < pixelToRegion.width-1; x++ , indexImg++ ) {
int regionA = pixelToRegion.data[indexImg];
// x + 1 , y
int regionB = pixelToRegion.data[indexImg+1];
// x , y + 1
int regionC = pixelToRegion.data[indexImg+pixelToRegion.stride];
// x + 1 , y + 1
int regionD = pixelToRegion.data[indexImg+1+pixelToRegion.stride];
// x - 1 , y + 1
int regionE = pixelToRegion.data[indexImg-1+pixelToRegion.stride];
boolean pruneA = segmentPruneFlag.data[regionA];
if( regionA != regionB ) {
boolean pruneB = segmentPruneFlag.data[regionB];
if( pruneA ) {
Node n = pruneGraph.get(segmentToPruneID.get(regionA));
n.connect(regionB);
}
if( pruneB ) {
Node n = pruneGraph.get(segmentToPruneID.get(regionB));
n.connect(regionA);
}
}
if( regionA != regionC ) {
boolean pruneC = segmentPruneFlag.data[regionC];
if( pruneA ) {
Node n = pruneGraph.get(segmentToPruneID.get(regionA));
n.connect(regionC);
}
if( pruneC ) {
Node n = pruneGraph.get(segmentToPruneID.get(regionC));
n.connect(regionA);
}
}
if( regionA != regionD ) {
boolean pruneD = segmentPruneFlag.data[regionD];
if( pruneA ) {
Node n = pruneGraph.get(segmentToPruneID.get(regionA));
n.connect(regionD);
}
if( pruneD ) {
Node n = pruneGraph.get(segmentToPruneID.get(regionD));
n.connect(regionA);
}
}
if( regionA != regionE ) {
boolean pruneE = segmentPruneFlag.data[regionE];
if( pruneA ) {
Node n = pruneGraph.get(segmentToPruneID.get(regionA));
n.connect(regionE);
}
if( pruneE ) {
Node n = pruneGraph.get(segmentToPruneID.get(regionE));
n.connect(regionA);
}
}
}
}
}
protected void adjacentBorder(GrayS32 pixelToRegion) {
for( int y = 0; y < pixelToRegion.height-1; y++ ) {
int x = pixelToRegion.width-1;
int indexImg = pixelToRegion.startIndex + pixelToRegion.stride*y + x;
checkAdjacentAround(x,y,indexImg,pixelToRegion);
if( connect.length == 8 ) {
x = 0;
indexImg = pixelToRegion.startIndex + pixelToRegion.stride*y + x;
checkAdjacentAround(x,y,indexImg,pixelToRegion);
}
}
for( int x = 0; x < pixelToRegion.width; x++ ) {
int y = pixelToRegion.height-1;
int indexImg = pixelToRegion.startIndex + pixelToRegion.stride*y + x;
checkAdjacentAround(x,y,indexImg,pixelToRegion);
}
}
private void checkAdjacentAround(int x, int y, int indexImg ,GrayS32 pixelToRegion ) {
int regionA = pixelToRegion.data[indexImg];
for( int i = 0; i < connect.length; i++ ) {
Point2D_I32 p = connect[i];
if( !pixelToRegion.isInBounds(x+p.x,y+p.y))
continue;
int regionB = pixelToRegion.data[indexImg+p.y*pixelToRegion.stride + p.x];
if( regionA != regionB ) {
boolean pruneA = segmentPruneFlag.data[regionA];
boolean pruneB = segmentPruneFlag.data[regionB];
if( pruneA ) {
Node n = pruneGraph.get(segmentToPruneID.get(regionA));
n.connect(regionB);
}
if( pruneB ) {
Node n = pruneGraph.get(segmentToPruneID.get(regionB));
n.connect(regionA);
}
}
}
}
/**
* Examine edges for the specified node and select node which it is the best match for it to merge with
*
* @param pruneId The prune Id of the segment which is to be merged into another segment
* @param regionColor List of region colors
*/
protected void selectMerge( int pruneId , FastQueue<float[]> regionColor ) {
// Grab information on the region which is being pruned
Node n = pruneGraph.get(pruneId);
float[] targetColor = regionColor.get(n.segment);
// segment ID and distance away from the most similar neighbor
int bestId = -1;
float bestDistance = Float.MAX_VALUE;
// Examine all the segments it is connected to to see which one it is most similar too
for( int i = 0; i < n.edges.size; i++ ) {
int segment = n.edges.get(i);
float[] neighborColor = regionColor.get(segment);
float d = SegmentMeanShiftSearch.distanceSq(targetColor, neighborColor);
if( d < bestDistance ) {
bestDistance = d;
bestId = segment;
}
}
if( bestId == -1 )
throw new RuntimeException("No neighbors? Something went really wrong.");
markMerge(n.segment, bestId);
}
/**
* Node in a graph. Specifies which segments are adjacent to a segment which is to be pruned.
*/
public static class Node
{
public int segment;
// List of segments this segment is connected to
public GrowQueue_I32 edges = new GrowQueue_I32();
public void init( int segment ) {
this.segment = segment;
edges.reset();
}
public void connect(int segment) {
if( isConnected(segment))
return;
this.edges.add(segment);
}
public boolean isConnected( int segment ) {
for( int i = 0; i < edges.size; i++ ) {
if( edges.data[i] == segment)
return true;
}
return false;
}
}
}