MATLAB: Outer and inner contour of the image from the centroid

convex hulldigital image processingimageimage analysisimage processingImage Processing Toolboximage segmentation

Hello everybody,

I have following image:

 I would like to find the Outer and inner contour of the image from the centroid, for example as here:

I would appreciate any help!

Thanks in advance!

Best Answer

Use bwconvhull() and then bwboundaries(). The outer is the boundaries of the convex hull. To get the inner, subtract or XOR the original from the convex hull, then call bwboundaries().

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MATLAB: Detect and Fill Edges of a Binary Image

Assuming that the inner/outer ring can be approximated by the edge of convex hull of inner/outer ring points, the area between inner and outer ring can be extracted by the following:

% Read and prepare the binary image
I = imread('Slice.jpg');
Igray = rgb2gray(I);
BWin = imbinarize(Igray);
BWin = imclearborder(BWin);
% Convex hull of outer ring points
CH1 = bwconvhull(BWin);
% Remove outer ring points
se = strel('disk',10);
CH1b = imerode(CH1,se);
BW1 = BWin & CH1b;
% Convex hull of inner ring points
CH2 = bwconvhull(BW1);
% Extract the area between inner and outer convex hull
BWout = CH1 - CH2;
% Show the result
figure
imshowpair(BWin,BWout)

MATLAB: I have plotted a image using imshow(Image). Now I placed “hold on” command. I have drawn the boundaries of each object in the image as given in code below. How to capture the new image with boundaries drawn in the plot into an array of pixels ?

Just assign them to an image in a loop inside the loop:

for k=1:length(B)
    boundary = B{k};
    for k = 1 : size(boundary, 1)
        x = boundary(:,2); % Column
        y = boundary(:,1); % Row
        boundaryImage(y, x) = 255;
    end
end

Best Answer

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MATLAB: Detect and Fill Edges of a Binary Image

MATLAB: I have plotted a image using imshow(Image). Now I placed “hold on” command. I have drawn the boundaries of each object in the image as given in code below. How to capture the new image with boundaries drawn in the plot into an array of pixels ?

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