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fix a bug in RANSAC that allowed inconsistent correspondences (usuall…
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…y only an issue with AffineModel
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@StephanPreibisch
StephanPreibisch committed May 10, 2024
1 parent 50b7e73 commit 4e3d637
Showing 1 changed file with 142 additions and 20 deletions.
162 changes: 142 additions & 20 deletions ...t/preibisch/mvrecon/process/interestpointregistration/pairwise/methods/ransac/RANSAC.java
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Original file line number Diff line number Diff line change
Expand Up @@ -24,15 +24,20 @@

import java.text.NumberFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map.Entry;

import mpicbg.models.Model;
import mpicbg.models.NotEnoughDataPointsException;
import mpicbg.models.PointMatch;
import net.preibisch.legacy.mpicbg.PointMatchGeneric;
import net.preibisch.mvrecon.fiji.ImgLib2Temp.Pair;
import net.preibisch.mvrecon.fiji.ImgLib2Temp.ValuePair;
import net.preibisch.mvrecon.fiji.spimdata.interestpoints.InterestPoint;
import net.preibisch.mvrecon.process.pointcloud.pointdescriptor.LinkedPoint;
import mpicbg.models.Model;
import mpicbg.models.NotEnoughDataPointsException;
import mpicbg.models.PointMatch;

/**
*
Expand All @@ -41,9 +46,9 @@
*/
public class RANSAC
{
public static < I extends InterestPoint > Pair< String, Double > computeRANSAC(
final ArrayList< PointMatchGeneric < I > > correspondenceCandidates,
final ArrayList< PointMatchGeneric < I > > inlierList,
public static < I extends InterestPoint > Pair< String, Double > computeRANSAC(
final ArrayList< PointMatchGeneric < I > > correspondenceCandidates,
final ArrayList< PointMatchGeneric < I > > inlierList,
final Model<?> model,
final double maxEpsilon,
final double minInlierRatio,
Expand All @@ -52,12 +57,6 @@ public static < I extends InterestPoint > Pair< String, Double > computeRANSAC(
{
final int numCorrespondences = correspondenceCandidates.size();
final int minNumCorrespondences = Math.max( model.getMinNumMatches(), (int)Math.round( model.getMinNumMatches() * minNumberInlierFactor ) );

/*
* First remove the inconsistent correspondences
*/
// I do not think anymore that this is required
// removeInconsistentCorrespondences( correspondenceCandidates );

// if there are not enough correspondences for the used model
if ( numCorrespondences < minNumCorrespondences )
Expand All @@ -67,9 +66,8 @@ public static < I extends InterestPoint > Pair< String, Double > computeRANSAC(
* The ArrayList that stores the inliers after RANSAC, contains PointMatches of LinkedPoints
* so that MultiThreading is possible
*/
//final ArrayList< PointMatchGeneric<LinkedPoint<T>> > candidates = new ArrayList<PointMatchGeneric<LinkedPoint<T>>>();
final ArrayList< PointMatch > candidates = new ArrayList< PointMatch >();
final ArrayList< PointMatch > inliers = new ArrayList< PointMatch >();
ArrayList< PointMatch > candidates = new ArrayList< PointMatch >();
ArrayList< PointMatch > inliers = new ArrayList< PointMatch >();

// clone the beads for the RANSAC as we are working multithreaded and they will be modified
for ( final PointMatchGeneric< I > correspondence : correspondenceCandidates )
Expand Down Expand Up @@ -105,24 +103,57 @@ public static < I extends InterestPoint > Pair< String, Double > computeRANSAC(
{
return new ValuePair< String, Double >( e.toString(), Double.NaN );
}

final NumberFormat nf = NumberFormat.getPercentInstance();
final double ratio = ( (double)inliers.size() / (double)candidates.size() );

if ( modelFound && inliers.size() >= minNumCorrespondences )
{
{
// remove the inconsistent inliers
final int numCorr = inliers.size();
inliers = removeInconsistentMatches( inliers );

if ( inliers.size() < minNumCorrespondences )
{
final int numRemoved = numCorr - inliers.size();

// and try again with cleaned correspondences
candidates = removeInconsistentMatches( candidates );
inliers.clear();

try
{
modelFound = model.filterRansac(
candidates,
inliers,
numIterations,
maxEpsilon, minInlierRatio );
}
catch ( NotEnoughDataPointsException e )
{
return new ValuePair< String, Double >( e.toString(), Double.NaN );
}

if ( !modelFound || inliers.size() < minNumCorrespondences )
return new ValuePair< String, Double >( "NO Model found after removing " + numRemoved + " inconsistent matches and re-running RANSAC using " + candidates.size(), Double.NaN );
}

for ( final PointMatch pointMatch : inliers )
{
@SuppressWarnings("unchecked")
final PointMatchGeneric<LinkedPoint< I > > pm = (PointMatchGeneric< LinkedPoint< I > >) pointMatch;

final I detectionA = pm.getPoint1().getLinkedObject();
final I detectionB = pm.getPoint2().getLinkedObject();

inlierList.add( new PointMatchGeneric< I >( detectionA, detectionB ) );
}

return new ValuePair< String, Double >( "Remaining inliers after RANSAC: " + inliers.size() + " of " + candidates.size() + " (" + nf.format(ratio) + ") with average error " + model.getCost(), model.getCost() );
String inconsistent = "";
if ( numCorr != inliers.size() )
inconsistent = " [removed " + (numCorr - inliers.size() ) + " inconsistent inliers]";

return new ValuePair< String, Double >( "Remaining inliers after RANSAC: " + inliers.size() + " of " + candidates.size() + " (" + nf.format(ratio) + ") with average error " + model.getCost() + "" + inconsistent, model.getCost() );
}
else
{
Expand All @@ -132,4 +163,95 @@ public static < I extends InterestPoint > Pair< String, Double > computeRANSAC(
return new ValuePair< String, Double >( "NO Model found after RANSAC of " + candidates.size(), Double.NaN );
}
}

/**
* a class that computes hash and equals only using the coordinates of a double[] array
*/
private static class HashableDoubleArray
{
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + Arrays.hashCode(l);
return result;
}

@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
HashableDoubleArray other = (HashableDoubleArray) obj;
return Arrays.equals(l, other.l);
}

final double[] l;

public HashableDoubleArray( final double[] l ) { this.l = l; }
}

public static < P extends PointMatch > ArrayList< P > removeInconsistentMatches( final List< P > matches )
{
final HashMap< HashableDoubleArray, ArrayList< Integer > > p1 = new HashMap<>();
final HashMap< HashableDoubleArray, ArrayList< Integer > > p2 = new HashMap<>();

for ( int i = 0; i < matches.size(); ++i )
{
final P pm = matches.get( i );

// only the underlying detections are the same objects
final HashableDoubleArray detectionA = new HashableDoubleArray( pm.getP1().getL() );
final HashableDoubleArray detectionB = new HashableDoubleArray( pm.getP2().getL() );

//System.out.println( Arrays.toString( detectionA.l ) + " " + Arrays.toString( detectionB.l ) + " " + detectionA.hashCode() + " = " + detectionB.hashCode() );

if ( p1.containsKey( detectionA ) )
{
p1.get( detectionA ).add( i );
}
else
{
final ArrayList<Integer> list = new ArrayList<>();
list.add( i );
p1.put( detectionA, list );
}

if ( p2.containsKey( detectionB ) )
{
p2.get( detectionB ).add( i );
}
else
{
final ArrayList<Integer> list = new ArrayList<>();
list.add( i );
p2.put( detectionB, list );
}
}

// build a HashSet of all indicies that collide
final HashSet< Integer > toRemove = new HashSet<>();

for ( final Entry< HashableDoubleArray, ArrayList< Integer > > entry : p1.entrySet() )
if (entry.getValue().size() > 1 )
toRemove.addAll( entry.getValue() );

for ( final Entry< HashableDoubleArray, ArrayList< Integer > > entry : p2.entrySet() )
if (entry.getValue().size() > 1 )
toRemove.addAll( entry.getValue() );

//System.out.println( "Removing " + toRemove.size() + " matches." );

final ArrayList< P > newList = new ArrayList<>();
for ( int i = 0; i < matches.size(); ++i )
{
if ( !toRemove.contains( i ) )
newList.add( matches.get( i ) );
}

return newList;
}
}

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