To perform image segmentation using the watershed algorithm in MATLAB while minimizing over-segmentation

To perform image segmentation using the watershed algorithm in MATLAB while minimizing over-segmentation, follow these steps:

Step-by-Step Explanation and Code

Read and Convert the Image to Grayscale

% Read the image
I = imread('coins.png');
% Convert to grayscale if necessary
if size(I, 3) == 3
    I = rgb2gray(I);
end

Compute Gradient Magnitude

% Calculate gradient magnitude
[Gmag, ~] = imgradient(I);

Morphological Preprocessing to Identify Markers

Smooth the Image using morphological operations to remove noise.

se = strel('disk', 20);
I_opened = imopen(I, se);
I_closed = imclose(I_opened, se);

Identify Foreground Markers using regional maxima.

fgm = imregionalmax(I_closed);
fgm = imclearborder(fgm); % Remove edge artifacts
fgm = bwareaopen(fgm, 20); % Remove small regions

Identify Background Markers using thresholding and distance transform.

bw = imbinarize(I_closed);
D = bwdist(bw);
DL = watershed(D);
bgm = DL == 0; % Watershed ridge lines as background

Impose Markers on Gradient Magnitude

% Combine foreground and background markers
modified_grad = imimposemin(Gmag, fgm | bgm);

Apply Watershed Algorithm
matlab

Copy
```
L = watershed(modified_grad);
```

Visualize the Result

% Convert labels to RGB for visualization
Lrgb = label2rgb(L, 'jet', 'w', 'shuffle');
figure;
imshow(Lrgb);
title('Watershed Segmentation with Markers');

% Overlay watershed boundaries on original image
boundaries = L == 0;
superimposed = imoverlay(I, boundaries, [1 0 0]);
figure;
imshow(superimposed);
title('Segmentation Overlay');

Key Considerations:

Morphological Structuring Element Size: Adjust the disk size (strel('disk', N)) based on object sizes in your image.
Marker Refinement: Use imregionalmax, imclearborder, and bwareaopen to clean up markers.
Gradient Modification: imimposemin ensures only the specified markers are treated as minima, controlling segmentation.

Step-by-Step Explanation and Code

Key Considerations:

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