validcorner

 VALIDCORNER checks if the input corner belongs to a chessboard.
 
 VALIDCORNER is used to indicate if a corner is a chessboard corner. It
 takes as input the cropped image and cropped edge image around the 
 corner. To ensure fast program execution sweepmatx and sweepmaty have
 been used. They are necessary input to this function.
 
 USAGE:
     [valid,peaklocs]=validcorner(img,imgedge,sweepmatx,sweepmaty);
 
 INPUTS:
     img: cropped grayscale image
 
     imgedge: cropped Sobel edge image
 
     sweepmatx: cropped sweepmatrix x, this is used for fast radial summation
 
     sweepmatx: cropped sweepmatrix y, this is used for fast radial summation
 
 
 OUTPUTS
     valid: scalar indicating wether the point is a chessboard corner of not, 1: yes, 0: no
 
     peaklocs: required by GETGRID

0001 function [valid,peaklocs]=validcorner(img,imgedge,sweepmatx,sweepmaty,debug)
0002 % VALIDCORNER checks if the input corner belongs to a chessboard.
0003 %
0004 % VALIDCORNER is used to indicate if a corner is a chessboard corner. It
0005 % takes as input the cropped image and cropped edge image around the
0006 % corner. To ensure fast program execution sweepmatx and sweepmaty have
0007 % been used. They are necessary input to this function.
0008 %
0009 % USAGE:
0010 %     [valid,peaklocs]=validcorner(img,imgedge,sweepmatx,sweepmaty);
0011 %
0012 % INPUTS:
0013 %     img: cropped grayscale image
0014 %
0015 %     imgedge: cropped Sobel edge image
0016 %
0017 %     sweepmatx: cropped sweepmatrix x, this is used for fast radial summation
0018 %
0019 %     sweepmatx: cropped sweepmatrix y, this is used for fast radial summation
0020 %
0021 %
0022 % OUTPUTS
0023 %     valid: scalar indicating wether the point is a chessboard corner of not, 1: yes, 0: no
0024 %
0025 %     peaklocs: required by GETGRID
0026 
0027 % validcorner parameters
0028 imadjsca=0.8; % larger adjust scalars corresponds to less adjustment
0029 imeadjsca=1.8;
0030 intth=0.5;
0031 
0032 
0033 if ~exist('debug','var') || isempty(debug)
0034     debug=0;
0035 end
0036 
0037 peaklocs=[];
0038 
0039 if debug
0040     close all;
0041 end
0042 
0043 %Adjust windowed image
0044 imgedge=adjimg(imgedge,imeadjsca); %edge images need less adjustment than imgn
0045 
0046 if debug
0047     figure;imshow(imgedge);
0048 end
0049 
0050 [theta,edgevalue,thetasmd,edgevaluesmd]=circsweep(imgedge,sweepmatx,sweepmaty);
0051 
0052 
0053 
0054 maxtab=peakdet(edgevalue);
0055 
0056 
0057 if size(maxtab,1)~=4      %Check if peaks equal 4
0058     valid=0;
0059     return;
0060 end
0061 
0062 peaklocs=maxtab(:,1);
0063 
0064 maxtabsmd=peakdet(edgevaluesmd);
0065 if size(maxtabsmd,1)~=2      %Check if peaks equal 2
0066     valid=0;
0067     return;
0068 end
0069 
0070 
0071 img=adjimg(img,imadjsca);
0072 [theta,intvalue,thetasmd,intvaluesmd]=circsweep(img,sweepmatx,sweepmaty);
0073 % intth=(max(intvaluesmd)-min(intvaluesmd))/2;
0074 
0075 %Work with summed arrays
0076 peaks=maxtabsmd(:,2);
0077 locs=maxtabsmd(:,1);
0078 
0079 
0080 peaks=peaks';
0081 locs=locs';
0082 
0083 % sort peak locations
0084 locs=sort(locs);
0085 
0086 
0087 crn1=mean(intvaluesmd([1:locs(1),locs(2):length(intvaluesmd)]));
0088 crn2=mean(intvaluesmd(locs(1):locs(2)));
0089 
0090 
0091 %Check if squares have enough intensity difference
0092 if abs(crn1-crn2)>intth
0093     valid=1;
0094 else
0095     valid=0;
0096 end