Hello, there is no error message regarding my code but the program is busy forever. what id the problem?

im = imread('retina.png');
im=rgb2gray(im);
S=size(im);
numR=S(1);
numC=S(2);  %now without  edges
 
%Voting
Accumulator = zeros(S); % initialize the accumulator
[yIndex ,xIndex] = find(im); % find x,y of edge pixels
r=30; r2 = r^2; % square of radius, to prevent its calculation in the loop
for cnt = 1:numel(xIndex)
    low=xIndex(cnt)-r;
    high=xIndex(cnt)+r;
    
    if (low<1) 
        low=1; 
    end
    
    if (high>numC)
        high=numC; 
    end
    
    for x0 = low:high
        yOffset = sqrt(r2-(xIndex(cnt)-x0)^2);
        y01 = round(yIndex(cnt)-yOffset);
        y02 = round(yIndex(cnt)+yOffset);
                
        if y01 < numR && y01 >= 1
            Accumulator(y01,x0) = Accumulator(y01,x0)+1;
        end
        
        if y02 < numR && y02 >= 1
            Accumulator(y02,x0) = Accumulator(y02,x0)+1;
%            rectangle('position',[x y 1 1],'EdgeColor','r');      
  
        end
    end
end
% Finding local maxima in Accumulator
thresh=4;
y0detect = []; x0detect = [];
AccumulatorbinaryMax = imregionalmax(Accumulator);
[Potential_y0 ,Potential_x0] = find(AccumulatorbinaryMax == 1);
Accumulatortemp = Accumulator - thresh;
for cnt = 1:numel(Potential_y0)
    if Accumulatortemp(Potential_y0(cnt),Potential_x0(cnt)) >= 0
        y0detect = [y0detect;Potential_y0(cnt)];
        x0detect = [x0detect;Potential_x0(cnt)];
        
    end
end
figure,imshow(im);
 
 for i=1:length(x0detect)
     x0=x0detect(i);
     y0=x0detect(i);
     
     for x=1:numC
         y=round(y0-sqrt(r2-(x-x0)^2));
         if y<=numR && y>=1
              rectangle('position',[x y 1 1],'EdgeColor','r');
         end
     end
 end 

[madhan ravi]

Try using logical indexing to avoid loops

Answer 1

[Cris LaPierre]

You are looping through every pixel in the image. Your comment (% find x,y of edge pixels) makes me think this may be unintentional. That is going to take a while.

There are also several nested for loops, which add to the run time.

You may try seeing if you can take advantage of matrix math to eliminate some of them.

Answer 2

[Image Analyst]

Not really sure what you're doing due to lack of comments but I see where you're trying to dynamically enlarge an array:

y0detect = [y0detect;Potential_y0(cnt)];

That takes a lot of time. You might try to preallocate y0detect and x0detect at their maximum expected size, then crop afterwards to the actual size.