Save plotted lines in an matrix

Here's my code to obtain these two lines:

[B,L,N,A] = bwboundaries(ImgClosed); 
figure
imshow(ImgClosed)
hold on; 
% Loop through object boundaries  
for k = 1:N 
    % Boundary k is the parent of a hole if the k-th column of the adjacency matrix A contains a non-zero element 
    if (nnz(A(:,k)) > 0) 
        boundary = B{k}; 
        plot(boundary(:,2),boundary(:,1),'r','LineWidth',2); 
        % Loop through the children of boundary k 
        for l = find(A(:,k))' 
            boundary = B{l}; 
            plot(boundary(:,2),boundary(:,1),'g','LineWidth',2); 
        end 
    end 
end

As ImgClosed is the binary image of the object I'm analysing.

And this is the result:

I want to save both lines (red and green) in an unique matrix so i can plot them again on top of another image. How can i save them?

Answer 1

[Kevin Holly]

You can save the plot and extract the XData and YData from it's subfields as shown below.

[B,L,N,A] = bwboundaries(ImgClosed); 
figure
imshow(ImgClosed)
hold on; 
% Loop through object boundaries  
for k = 1:N 
    % Boundary k is the parent of a hole if the k-th column of the adjacency matrix A contains a non-zero element 
    if (nnz(A(:,k)) > 0) 
        boundary = B{k}; 
        redline = plot(boundary(:,2),boundary(:,1),'r','LineWidth',2); 
        % Loop through the children of boundary k 
        for l = find(A(:,k))' 
            boundary = B{l}; 
            greenline = plot(boundary(:,2),boundary(:,1),'g','LineWidth',2); 
        end 
    end 
end

figure
axes
plot(redline.XData,redline.YData,'r','LineWidth',2)
hold on
plot(greenline.XData,greenline.YData,'g','LineWidth',2); 

[Bruno Neto]

The thing is: I need to constrain a delaunay triangulation using those contours. And with that I'm still not able to do it properly

DT = delaunayTriangulation(x,y,C)

The C in the code above, should be my contours (both red and green lines mentioned before)

[Kevin Holly]

ImgClosed = imread('test.png');
ImgClosed=im2bw(ImgClosed);

[B,L,N,A] = bwboundaries(ImgClosed); 
figure
imshow(ImgClosed)
hold on; 
for k = 1:N
    % Boundary k is the parent of a hole if the k-th column of the adjacency matrix A contains a non-zero element
    if (nnz(A(:,k)) > 0)
        boundary = B{k};
        redline = plot(boundary(:,2),boundary(:,1),'r','LineWidth',2);
        % Loop through the children of boundary k
        for l = find(A(:,k))'
            boundary = B{l};
            greenline(l,:) = plot(boundary(:,2),boundary(:,1),'g','LineWidth',2);
        end
    end
end

figure
axes
plot(redline.XData,redline.YData,'r','LineWidth',2)
hold on
x=redline.XData;
y=redline.YData;
c = [(1:length(x)-1).' (2:length(x)).'];

for jj = 1:size(greenline,1)
    try
        plot(greenline(jj).XData,greenline(jj).YData,'g','LineWidth',2);
        x_start = length(x);
        x=[x greenline(jj).XData];
        y=[y greenline(jj).YData];
        c = [c;(x_start+(1:length(greenline(jj).XData)-1)).' (x_start+(2:length(greenline(jj).XData))).'];
    catch
    end
end

DT = delaunayTriangulation(x',y',c);

Warning: Duplicate data points have been detected and removed.
The Triangulation indices and constraints are defined with respect to the unique set of points in delaunayTriangulation.

% IC = incenter(DT);
triplot(DT)

figure
DT = delaunayTriangulation(x',y',c);

Warning: Duplicate data points have been detected and removed.
The Triangulation indices and constraints are defined with respect to the unique set of points in delaunayTriangulation.

IO = isInterior(DT);
triplot(DT(IO, :),DT.Points(:,1), DT.Points(:,2),'LineWidth', 2)

[Bruno Neto]

Thank you so much! Is there anyway I can densify the triangles inside the object? So I can get something like the delaunay triangulation I showed above?

[Kevin Holly]

I was able to do so and posted the results here.