Can anyone please explain the meaning of below code?

[rows, columns] = size(grayImage);
circleCenterX = 120; 
circleCenterY = 120; % square area 0f 500*500 
circleRadius = 110;    % big circle radius 
circleImage = false(rows, columns); 
[x, y] = meshgrid(1:columns, 1:rows); 
circleImage((x - circleCenterX).^2 + (y - circleCenterY).^2 <= circleRadius.^2) = true;
b = and(circleImage,b);
labeledImage = bwlabel(b);
measurements = regionprops(labeledImage, 'BoundingBox', 'Area');
matrix = zeros(4,length(measurements));
vector = zeros(1,length(measurements));
for k = 1 : length(measurements)
thisBB = measurements(k).BoundingBox;
matrix(:,k) = thisBB(:);
vector(k) = thisBB(2);
rectangle('Position', [thisBB(1),thisBB(2),thisBB(3),thisBB(4)],...
'EdgeColor','g','LineWidth',2 )
end
vector = sort(vector);

Answer 1

[Walter Roberson]

The code creates a binary mask which is the inside of a circle of radius 110, centered at (120, 120). It then "ands" that mask with b, which has the effect of erasing everything in b that is outside the circle.

Components of the result are then labeled, and bounding boxes and area are found. The bounding boxes and area are recorded in the arrays "matrix" and "vector", and rectangles are plotted corresponding to each bounding box.

Finally, the areas are sorted -- but the original order is not kept track of, so it is not possible to associate the sorted areas with the corresponding bounding box. That final line

vector = sort(vector);

should be replaced by

[vector, sortorder] = sort(vector);
matrix = matrix(sortorder, :);

After that, the order of the bounding boxes would correspond to increasing area.

[Manjiree Waikar]

Thank you so much sir. It helped me to understand very easily.