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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.shapes.polygon;
import boofcv.alg.InputSanityCheck;
import boofcv.alg.distort.DistortImageOps;
import boofcv.alg.filter.binary.Contour;
import boofcv.alg.filter.binary.LinearContourLabelChang2004;
import boofcv.alg.shapes.edge.PolygonEdgeIntensity;
import boofcv.alg.shapes.polyline.MinimizeEnergyPrune;
import boofcv.alg.shapes.polyline.RefinePolyLineCorner;
import boofcv.alg.shapes.polyline.SplitMergeLineFitLoop;
import boofcv.struct.ConnectRule;
import boofcv.struct.distort.PixelTransform_F32;
import boofcv.struct.image.ImageSInt32;
import boofcv.struct.image.ImageSingleBand;
import boofcv.struct.image.ImageUInt8;
import georegression.geometry.UtilPolygons2D_F64;
import georegression.metric.Area2D_F64;
import georegression.struct.point.Point2D_F64;
import georegression.struct.point.Point2D_I32;
import georegression.struct.shapes.Polygon2D_F64;
import georegression.struct.shapes.RectangleLength2D_F32;
import org.ddogleg.struct.FastQueue;
import org.ddogleg.struct.GrowQueue_B;
import org.ddogleg.struct.GrowQueue_I32;
import java.util.ArrayList;
import java.util.List;
/**
*
* Detects convex polygons with the specified number of sides in an image. Shapes are assumed to be black shapes
* against a white background, allowing for thresholding to be used. Subpixel refinement is done using the
* provided implementation of {@link RefineBinaryPolygon}.
*
*
* Processing Steps:
*
* - First the input a gray scale image and a binarized version of it.
* - The contours of black blobs are found.
* - From the contours polygons are fitted and refined to pixel accuracy.
* - (Optional) Sub-pixel refinement of the polygon's edges and/or corners.
*
*
*
* The returned polygons will encompass the entire black polygon. Here is a simple example in 1D. If all pixels are
* white, but pixels ranging from 5 to 10, inclusive, then the returned boundaries would be 5.0 to 11.0. This
* means that coordinates 5.0 ≤ x < 11.0 are all black. 11.0 is included, but note that the entire pixel 11 is white.
*
*
* @author Peter Abeles
*/
public class BinaryPolygonDetector {
// minimum size of a shape's contour as a fraction of the image width
private double minContourFraction;
private int minimumContour; // this is image.width*minContourFraction
private double minimumArea; // computed from minimumContour
// does the polygon have to be convex
private boolean convex;
private LinearContourLabelChang2004 contourFinder = new LinearContourLabelChang2004(ConnectRule.FOUR);
private ImageSInt32 labeled = new ImageSInt32(1,1);
// finds the initial polygon around a target candidate
private SplitMergeLineFitLoop fitPolygon;
// removes extra corners
GrowQueue_I32 pruned = new GrowQueue_I32();
MinimizeEnergyPrune pruner;
// Improve the selection of corner pixels in the contour
private RefinePolyLineCorner improveContour = new RefinePolyLineCorner(true,20);
// Refines the estimate of the polygon's lines using a subpixel technique
private RefineBinaryPolygon refinePolygon;
// List of all squares that it finds
private FastQueue found = new FastQueue(Polygon2D_F64.class,true);
// extera information for found shapes
private FastQueue foundInfo = new FastQueue(Info.class,true);
// type of input image
private Class inputType;
// number of lines allowed in the polygon
private int minSides,maxSides;
// true if points touching the border are NOT pruned
private boolean canTouchBorder;
// work space for initial polygon
private Polygon2D_F64 workPoly = new Polygon2D_F64();
// should the order of the polygon be on clockwise order on output?
private boolean outputClockwise;
// storage for the contours associated with a found target. used for debugging
// All contours are in distorted pixel coordiantes
private List foundContours = new ArrayList();
// transforms which can be used to handle lens distortion
protected PixelTransform_F32 distToUndist, undistToDist;
boolean verbose = false;
// used to remove false positives
PolygonEdgeIntensity edgeIntensity;
double edgeThreshold;
// should it check the edge score before? With a chessboard pattern the initial guess is known to be very poor
// so it should only check the edge after. Otherwise its good to filter before optimization.
boolean checkEdgeBefore = true;
// helper used to customize low level behaviors internally
private PolygonHelper helper;
// storage for contour in undistorted image pixels
private FastQueue contourUndist = new FastQueue(Point2D_I32.class,true);
/**
* Configures the detector.
* @param minSides minimum number of sides
* @param maxSides maximum number of sides
* @param contourToPolygon Fits a crude polygon to the shape's binary contour
* @param refinePolygon (Optional) Refines the polygon's lines. Set to null to skip step
* @param minContourFraction Size of minimum contour as a fraction of the input image's width. Try 0.23
* @param outputClockwise If true then the order of the output polygons will be in clockwise order
* @param convex If true it will only return convex shapes
* @param touchBorder if true then shapes which touch the image border are allowed
* @param splitPenalty Penalty given to a line segment while splitting. See {@link MinimizeEnergyPrune}
* @param edgeThreshold Polygons with an edge intensity less than this are discarded.
* @param inputType Type of input image it's processing
*/
public BinaryPolygonDetector(int minSides, int maxSides,
SplitMergeLineFitLoop contourToPolygon,
RefineBinaryPolygon refinePolygon,
double minContourFraction,
boolean outputClockwise,
boolean convex,
boolean touchBorder, double splitPenalty,
double edgeThreshold,
Class inputType) {
setNumberOfSides(minSides,maxSides);
this.refinePolygon = refinePolygon;
this.edgeIntensity = new PolygonEdgeIntensity(1,1.5,15,inputType);
this.inputType = inputType;
this.minContourFraction = minContourFraction;
this.fitPolygon = contourToPolygon;
this.outputClockwise = outputClockwise;
this.convex = convex;
this.canTouchBorder = touchBorder;
this.edgeThreshold = edgeThreshold;
pruner = new MinimizeEnergyPrune(splitPenalty);
workPoly = new Polygon2D_F64(1);
}
/**
* Specifies transforms which can be used to change coordinates from distorted to undistorted and the opposite
* coordinates. The undistorted image is never explicitly created.
*
*
* WARNING: The undistorted image must have the same bounds as the distorted input image. This is because
* several of the bounds checks use the image shape. This are simplified greatly by this assumption.
*
*
* @param width Input image width. Used in sanity check only.
* @param height Input image height. Used in sanity check only.
* @param distToUndist Transform from distorted to undistorted image.
* @param undistToDist Transform from undistorted to distorted image.
*/
public void setLensDistortion( int width , int height ,
PixelTransform_F32 distToUndist , PixelTransform_F32 undistToDist ) {
this.distToUndist = distToUndist;
this.undistToDist = undistToDist;
// sanity check since I think many people will screw this up.
RectangleLength2D_F32 rect = DistortImageOps.boundBox_F32(width, height, distToUndist);
float x1 = rect.x0 + rect.width;
float y1 = rect.y0 + rect.height;
float tol = 1e-4f;
if( rect.getX() < -tol || rect.getY() < -tol || x1 > width+tol || y1 > height+tol ) {
throw new IllegalArgumentException("You failed the idiot test! RTFM! The undistorted image "+
"must be contained by the same bounds as the input distorted image");
}
if( refinePolygon != null ) {
refinePolygon.setLensDistortion(width, height, distToUndist, undistToDist);
}
edgeIntensity.setTransform(undistToDist);
}
/**
* Examines the undistorted gray scake input image for squares.
*
* @param gray Input image
*/
public void process(T gray, ImageUInt8 binary) {
if( verbose ) System.out.println("ENTER BinaryPolygonDetector.process()");
InputSanityCheck.checkSameShape(binary, gray);
if( labeled.width != gray.width || labeled.height == gray.width )
configure(gray.width,gray.height);
found.reset();
foundContours.clear();
foundInfo.reset();
edgeIntensity.setImage(gray);
findCandidateShapes(gray, binary);
if( verbose ) System.out.println("EXIT BinaryPolygonDetector.process()");
}
/**
* Specifies the image's intrinsic parameters and target size
*
* @param width Width of the input image
* @param height Height of the input image
*/
private void configure( int width , int height ) {
// resize storage images
labeled.reshape(width, height);
// adjust size based parameters based on image size
this.minimumContour = (int)(width*minContourFraction);
this.minimumArea = Math.pow(this.minimumContour /4.0,2);
if( helper != null )
helper.setImageShape(width,height);
}
/**
* Finds blobs in the binary image. Then looks for blobs that meet size and shape requirements. See code
* below for the requirements. Those that remain are considered to be target candidates.
*/
private void findCandidateShapes( T gray , ImageUInt8 binary ) {
int maxSidesConsider = (int)Math.ceil(maxSides*1.5);
// stop fitting the polygon if it clearly has way too many sides
fitPolygon.setAbortSplits(2*maxSides);
// find binary blobs
contourFinder.process(binary, labeled);
// find blobs where all 4 edges are lines
FastQueue blobs = contourFinder.getContours();
for (int i = 0; i < blobs.size; i++) {
Contour c = blobs.get(i);
if( c.external.size() >= minimumContour) {
// System.out.println("----- candidate "+c.external.size());
// ignore shapes which touch the image border
boolean touchesBorder = touchesBorder(c.external);
if( !canTouchBorder && touchesBorder ) {
if( verbose ) System.out.println("rejected polygon, touched border");
continue;
}
if( helper != null )
if( !helper.filterContour(c.external,touchesBorder,true) )
continue;
// remove lens distortion
List contourUndist;
if( distToUndist != null ) {
removeDistortionFromContour(c.external,this.contourUndist);
contourUndist = this.contourUndist.toList();
if( helper != null )
if( !helper.filterContour(contourUndist,touchesBorder,false) )
continue;
} else {
contourUndist = c.external;
}
if( !fitPolygon.process(contourUndist) ) {
if( verbose ) System.out.println("rejected polygon initial fit failed. contour size = "+c.external.size());
continue;
}
GrowQueue_I32 splits = fitPolygon.getSplits();
if( splits.size() > maxSidesConsider ) {
if( verbose ) System.out.println("Way too many corners, "+splits.size()+". Aborting before improve. Contour size "+c.external.size());
continue;
}
// Perform a local search and improve the corner placements
if( !improveContour.fit(contourUndist,splits) ) {
if( verbose ) System.out.println("rejected improve contour. contour size = "+c.external.size());
continue;
}
// reduce the number of corners based on an energy model
pruner.prune(c.external, splits, pruned);
splits = pruned;
// only accept polygons with the expected number of sides
if (!expectedNumberOfSides(splits)) {
// System.out.println("First point "+c.external.get(0));
if( verbose ) System.out.println("rejected number of sides. "+splits.size()+" contour "+c.external.size());
continue;
}
if( helper != null ) {
if( !helper.filterPixelPolygon(contourUndist,c.external,splits,touchesBorder) ) {
if( verbose ) System.out.println("rejected by helper.filterPixelPolygon()");
continue;
}
}
// convert the format of the initial crude polygon
workPoly.vertexes.resize(splits.size());
for (int j = 0; j < splits.size(); j++) {
Point2D_I32 p = contourUndist.get( splits.get(j));
workPoly.get(j).set(p.x,p.y);
}
if( helper != null ) {
helper.adjustBeforeOptimize(workPoly);
}
// Filter out polygons which are not convex if requested by the user
if( convex && !UtilPolygons2D_F64.isConvex(workPoly)) {
if( verbose ) System.out.println("Rejected not convex");
continue;
}
// make sure it's big enough
double area = Area2D_F64.polygonSimple(workPoly);
if( area < minimumArea ) {
if( verbose ) System.out.println("Rejected area");
continue;
}
// Test the edge quality and prune before performing an expensive optimization
if( checkEdgeBefore && !checkPolygonEdge(workPoly,workPoly.isCCW())) {
// if( verbose ) System.out.println("Rejected edge score before");
continue;
}
Polygon2D_F64 refined = found.grow();
refined.vertexes.resize(splits.size);
boolean success;
if( refinePolygon != null ) {
refinePolygon.setImage(gray);
success = refinePolygon.refine(workPoly,contourUndist,splits,refined);
if( verbose && !success ) System.out.println("Rejected after refinePolygon");
} else {
refined.set(workPoly);
success = true;
}
boolean refinedCCW = refined.isCCW();
// test it again with the full threshold
if( !checkPolygonEdge(refined,refinedCCW)) {
if( verbose ) System.out.println("Rejected edge score, after");
success = false;
}
// refine the polygon and add it to the found list
if( success ) {
if( outputClockwise == refinedCCW )
refined.flip();
// System.out.println("SUCCESS!!!\n");
c.id = found.size();
foundContours.add(c);
Info info = foundInfo.grow();
info.external = true;
info.borderCorners.reset();
if( touchesBorder ) {
// tolerance is a little bit above 0.5.pixels due to prior rounding to integer
determineCornersOnBorder(refined, info.borderCorners, 0.7f);
}
info.edgeInside = edgeIntensity.getAverageInside();
info.edgeOutside = edgeIntensity.getAverageOutside();
} else {
found.removeTail();
}
}
}
}
/**
* Check to see if corners are touching the image border
* @param polygon Refined polygon
* @param corners storage for corner indexes
*/
void determineCornersOnBorder( Polygon2D_F64 polygon , GrowQueue_B corners , float tol ) {
corners.reset();
for (int i = 0; i < polygon.size(); i++) {
corners.add(isUndistortedOnBorder(polygon.get(i),tol));
}
}
/**
* Coverts the point into distorted image coordinates and then checks to see if it is on the image border
* @param undistorted pixel in undistorted coordinates
* @param tol Tolerance for a point being on the image border
* @return true if on the border or false otherwise
*/
boolean isUndistortedOnBorder( Point2D_F64 undistorted , float tol ) {
float x,y;
if( undistToDist == null ) {
x = (float)undistorted.x;
y = (float)undistorted.y;
} else {
undistToDist.compute((int)Math.round(undistorted.x),(int)Math.round(undistorted.y));
x = undistToDist.distX;
y = undistToDist.distY;
}
return( x <= tol || y <= tol || x+tol >= labeled.width-1 || y+tol >= labeled.height-1 );
}
/**
* Checks to see if the edge is intense enough or if it should be discarded as noise
* @return true if the edge is strong enough
*/
private boolean checkPolygonEdge( Polygon2D_F64 polygon , boolean ccw ) {
if(!edgeIntensity.computeEdge(polygon,ccw)) {
if( verbose ) System.out.println("Can't compute polygon edge intensity");
return false;
}
if(!edgeIntensity.checkIntensity(true,edgeThreshold)) {
if( verbose ) {
double inside = edgeIntensity.getAverageInside();
double outside = edgeIntensity.getAverageOutside();
System.out.println("Rejected edge score inside: " + inside+" "+outside);
}
return false;
}
return true;
}
/**
* True if the number of sides found matches what it is looking for
*/
private boolean expectedNumberOfSides(GrowQueue_I32 splits) {
return splits.size() >= minSides && splits.size() <= maxSides;
}
/**
* Removes lens distortion from the found contour
*/
private void removeDistortionFromContour(List distorted, FastQueue undistorted ) {
undistorted.reset();
for (int j = 0; j < distorted.size(); j++) {
// remove distortion
Point2D_I32 p = distorted.get(j);
distToUndist.compute(p.x,p.y);
// round to minimize error
int x = Math.round(distToUndist.distX);
int y = Math.round(distToUndist.distY);
// save the results
undistorted.grow().set(x,y);
}
}
/**
* Checks to see if some part of the contour touches the image border. Most likely cropped
*/
protected final boolean touchesBorder( List contour ) {
int endX = labeled.width-1;
int endY = labeled.height-1;
for (int j = 0; j < contour.size(); j++) {
Point2D_I32 p = contour.get(j);
if( p.x == 0 || p.y == 0 || p.x == endX || p.y == endY )
{
return true;
}
}
return false;
}
public void setHelper(PolygonHelper helper) {
this.helper = helper;
}
public boolean isConvex() {
return convex;
}
public void setConvex(boolean convex) {
this.convex = convex;
}
public ImageSInt32 getLabeled() {
return labeled;
}
public boolean isOutputClockwise() {
return outputClockwise;
}
public FastQueue getFoundPolygons() {
return found;
}
public List getUsedContours(){return foundContours;}
public List getAllContours(){return contourFinder.getContours().toList();}
public Class getInputType() {
return inputType;
}
public void setNumberOfSides( int min , int max ) {
if( min < 3 )
throw new IllegalArgumentException("The min must be >= 3");
if( max < min )
throw new IllegalArgumentException("The max must be >= the min");
this.minSides = min;
this.maxSides = max;
}
public int getMinimumSides() {
return minSides;
}
public int getMaximumSides() {
return maxSides;
}
public void setVerbose(boolean verbose) {
this.verbose = verbose;
}
public boolean isCheckEdgeBefore() {
return checkEdgeBefore;
}
public RefineBinaryPolygon getRefinePolygon() {
return refinePolygon;
}
public void setRefinePolygon(RefineBinaryPolygon refinePolygon) {
this.refinePolygon = refinePolygon;
}
public double getEdgeThreshold() {
return edgeThreshold;
}
public void setEdgeThreshold(double edgeThreshold) {
this.edgeThreshold = edgeThreshold;
}
public PixelTransform_F32 getDistToUndist() {
return distToUndist;
}
public PixelTransform_F32 getUndistToDist() {
return undistToDist;
}
/**
* Returns additional information on the polygon
*/
public FastQueue getPolygonInfo() {
return foundInfo;
}
/**
* If set to true it will prune using polygons using their edge intensity before sub-pixel optimization.
* This should only be set to false if the initial edge is known to be off by a bit, like with a chessboard.
* @param checkEdgeBefore true for checking before and false for after.
*/
public void setCheckEdgeBefore(boolean checkEdgeBefore) {
this.checkEdgeBefore = checkEdgeBefore;
}
public static class Info
{
/**
* Was it created from an external or internal contour
*/
public boolean external;
/**
* Average pixel intensity score along the polygon's edge inside and outside
*/
public double edgeInside,edgeOutside;
/**
* Boolean value for each corner being along the border. If empty then non of the corners are long the border.
* true means the corner is a border corner.
*/
public GrowQueue_B borderCorners = new GrowQueue_B();
public boolean touchesBorder() {
if( borderCorners.size() == 0 )
return false;
else {
for (int i = 0; i < borderCorners.size(); i++) {
if( borderCorners.get(i))
return true;
}
}
return false;
}
}
}