Find peak (regions) in 2D data

Question

I am looking to find peak regions in 2D data (if you will, grayscale images or 2D landscapes, created through a Hough transform). By peak region I

Answer 1

In such peak finding problems, I mostly use morphological operations. Since the Hough transform results are mostly noisy, I prefer blurring it first, then apply tophat and extended maxima transform. Then for each local maximum, find the region around it with adaptive thresholding. Here is a sample code:

im=imread('udIuy.png');

% blur
im=imgaussfilt(im,1);

% tophat transform
im2=imtophat(im,strel('disk',5));

% extended maximums
im3=imextendedmax(im2,10);

% Extract each blob
s=regionprops(im3,'Centroid','PixelIdxList');

figure,imagesc(im),axis image

for i=1:numel(s)
    x=ceil(s(i).Centroid);
    tmp=im*0;
    tmp(s(i).PixelIdxList)=1;
    tmp2=tmp.*im2;

% The maximum amplitude and location

    [refV,b]=max(tmp2(:));
    [x2,y2]=ind2sub(size(im),b);

% select the region around local max amplitude    
    tmp=bwselect(im2>refV*0.6,y2,x2,4);  

    [xi,yi]=find(tmp);
    hold on, plot(yi,xi,'r.')
    hold on, text(y2+10,x2,num2str(i),'Color','white','FontSize',16)    
end