# How to mark specific points in a boundary?

4 views (last 30 days)
Nayana R on 20 Oct 2018
Commented: Image Analyst on 7 Mar 2020
I used this code to mark boundary of my image.Now I want to detect specific points such as most concave point in a specific region of the boundary and most convex point.I have given the image that i detect the boundary and i manually detect the points using blue arrows that i want to mark automatically.Can you please suggest a method for this?
figure()
imshow(I);colormap gray
title('Original Image','fontsize',14);
img2 = imnoise(I,'salt & pepper',0.025);
I1 = img2;
for c = 1 : 3
I1(:, :, c) = medfilt2(img2(:, :, c), [5, 5]);%add median filter
end
x =rgb2gray(I1);
I2 = x < 60;
%I2 = im2bw(I1);
figure()
imshow(I2);colormap gray
title('Median Filtererd','fontsize',14)
dim = size(I2);
col = round(dim(2)/2)-90;
row = find(I2(:,col), 1 );
boundary = bwtraceboundary(I2,[row, col],'N');
%----Display original grayscale image and use coordinates returned by bwtraceboundary to plot the border on the image.
imshow(I);
hold on;
plot(boundary(:,2),boundary(:,1),'r','LineWidth',1);
BW_filled = imfill(I2,'holes');
boundaries = bwboundaries(BW_filled);
%------Plot the borders of the original grayscale image using the coordinates returned by bwboundaries-----------
for k=1:10
b = boundaries{k};
plot(b(:,2),b(:,1),'r','LineWidth',1);
end

Image Analyst on 20 Oct 2018
Nayana R on 20 Oct 2018
Thank you for your reply Image Analyst.But I don't know how to run a function in MatLab as I am new to MatLab.I tried it.I can't understand what are arguments they are asking as (Vertices,Lines). Can you please explain a way to run this function if you can?
In my previous code above edges traced are not saving in the image.How can I save image with edges and apply this function to my own image?I hope you can help me.Thank you.

Jai Sri on 6 Mar 2020
How to mark boundary of gray scale image in original color image?
Image Analyst on 7 Mar 2020
This does not look like an answer to Nayana's question. If you have a question, post a new question and post both your gray scale image and your original color image.

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