How to use Watershed function to find multiple regions in a 2D array?

Hi There,

• I'm a newbie to Matlab and I'm wondering if there is a better or easier way to find multiple peak regions (I understand watershed follows the idea to find sinks so I just multiplied the data by -1). I'm following the method from link Marker-Controlled Watershed Segmentation Here is my code :

rgb = imread('vil_matlab_test.png');
I = rgb2gray(rgb);
hy = fspecial('sobel');
hx = hy';
Iy = imfilter(double(I), hy, 'replicate');
Ix = imfilter(double(I), hx, 'replicate');
gradmag = sqrt(Ix.^2 + Iy.^2);
se = strel('disk', 20);
Io = imopen(I, se);
Ie = imerode(I, se);
Iobr = imreconstruct(Ie, I);
Ioc = imclose(Io, se);
Iobrd = imdilate(Iobr, se);
Iobrcbr = imreconstruct(imcomplement(Iobrd), imcomplement(Iobr));
Iobrcbr = imcomplement(Iobrcbr);
fgm = imregionalmax(Iobrcbr);
I2 = I;
I2(fgm) = 255;
se2 = strel(ones(5,5));
fgm2 = imclose(fgm, se2);
fgm3 = imerode(fgm2, se2);
fgm4 = bwareaopen(fgm3, 20);
I3 = I;
I3(fgm4) = 255;
bw = imbinarize(Iobrcbr);
D = bwdist(bw);
DL = watershed(D);
bgm = DL == 0;
figure 
The input figure looks like :

I'm expecting to find at least two regions, but the result looks like :

Can anyone tell me how to correct this? Or is there other better way to do this? Thanks!