hough变换检测圆的matlab程序 1

function [y0detect,x0detect,Accumulator] = houghcircle(Imbinary,r,thresh)
%HOUGHCIRCLE - detects circles with specific radius in a binary image.
%
%Comments:
% Function uses Standard Hough Transform to detect circles in a binary image.
% According to the Hough Transform for circles, each pixel in image space
% corresponds to a circle in Hough space and vise versa.
% upper left corner of image is the origin of coordinate system.
%
%Usage: [y0detect,x0detect,Accumulator] = houghcircle(Imbinary,r,thresh)
%
%Arguments:
% Imbinary - a binary image. image pixels that have value equal to 1 are
% interested pixels for HOUGHLINE function.
% r - radius of circles.
% thresh - a threshold value that determines the minimum number of
% pixels that belong to a circle in image space. threshold must be
% bigger than or equal to 4(default).
%
%Returns:
% y0detect - row coordinates of detected circles.
% x0detect - column coordinates of detected circles.
% Accumulator - the accumulator array in Hough space.
%
%Written by :
% Amin Sarafraz
% Photogrammetry & Computer Vision Devision
% Geomatics Department,Faculty of Engineering
% University of Tehran,Iran
% sarafraz@geomatics.ut.ac.ir
%
%May 5,2004 - Original version
%November 24,2004 - Modified version,faster and better performance

if nargin == 2
thresh = 4;
elseif thresh < 4
error('treshold value must be bigger or equal to 4');
return
end

%Voting
Accumulator = zeros(size(Imbinary));
[yIndex xIndex] = find(Imbinary);
for cnt = 1:length(xIndex)
low=x-r;
high=x+r;
if (low<1) low=1; end
if (high>size(Imbinary,2)) high=size(Imbinary,2); end
for x0 = low:high
y01 = y-sqrt(r^2-(x-x0)^2);
y02 = y+sqrt(r^2-(x-x0)^2);
y01 = round(y01); y02 = round(y02);
if y01 < size(Imbinary,1) & y01 >= 1
Accumulator(y01,x0) = Accumulator(y01,x0)+1;
end
if y02 < size(Imbinary,1) & y02 >= 1
Accumulator(y02,x0) = Accumulator(y02,x0)+1;
end
end
%
% low=xIndex(cnt)-r;
% high=xIndex(cnt)+r;
% if (low<1) low=1; end
% if (high>size(Imbinary,2)) high=size(Imbinary,2); end
% for x0 = low:high
% y01 = yIndex(cnt)-sqrt(r^2-(xIndex(cnt)-x0)^2);
% y02 = yIndex(cnt)+sqrt(r^2-(xIndex(cnt)-x0)^2);
% y01 = round(y01); y02 = round(y02);
% if y01 < size(Imbinary,1) & y01 >= 1
% Accumulator(y01,x0) = Accumulator(y01,x0)+1;
% end
% if y02 < size(Imbinary,1) & y02 >= 1
% Accumulator(y02,x0) = Accumulator(y02,x0)+1;
% end
% end
end

% Finding local maxima in Accumulator
y0detect = []; x0detect = [];
AccumulatorbinaryMax = imregionalma
x(Accum

ulator);
[Potential_y0 Potential_x0] = find(AccumulatorbinaryMax == 1);
Accumulatortemp = Accumulator - thresh;
for cnt = 1:length(Potential_y0)
if Accumulatortemp(Potential_y0(cnt),Potential_x0(cnt)) >= 0
y0detect = [y0detect;Potential_y0(cnt)];
x0detect = [x0detect;Potential_x0(cnt)];
end
end