identify and remove objects outside of or touching the boundary in an image? in matlab

To identify objects outside of or touching the boundary in an image, you can use boundary tracing to generate a boundary mask, which can then be used to label objects that intersect with the boundary. You can then remove these objects using logical indexing.

main.m
% Load the image
I = imread('image.jpg');

% Generate a binary boundary mask using the Sobel edge detection
boundary_mask = edge(I, 'sobel');

% Dilate the boundary mask to ensure that objects crossing the boundary are accounted for
se = strel('disk', 4);
boundary_mask = imdilate(boundary_mask, se);

% Label the objects in the image
labeled = bwlabel(I);

% Identify objects intersecting with the boundary
objects_at_boundary = unique(labeled(boundary_mask));

% Remove objects intersecting with the boundary using logical indexing
cleaned = ismember(labeled, objects_at_boundary);
cleaned(boundary_mask) = 0;

% Display the cleaned image
imshow(cleaned);
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The code above loads an image 'image.jpg' and generates a binary boundary mask using the Sobel edge detection. This boundary mask is then dilated using a disk-shaped structuring element to include objects crossing the boundary.

The objects in the image are labeled using the bwlabel function, and objects intersecting with the boundary are identified using logical indexing with the ismember function. These objects are removed from the image using another logical indexing operation, and the result is displayed using imshow.