How can I find pixel coordinates of a perimeter in a binary image?
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Hi
I have a binary image which I have extracted the perimeter with bwperim() function. Now that I have the perimeter image I am trying to extract the coordinates of pixels in this perimeter.Here are the images:
The white perimeter illustrated in the second image is where I want to find the coordinates. Any Suggestions is appreciated.
Thanks
3 个评论
mahesh pawar
2017-3-3
Per = bwperim(img);
[r,c]=size(Per);
p=1;
z = nnz(Per);
cord = zeros(z,2);
for i=1:r
for j=1:c
if (Per(r,c)) == 1
cord(p,1)=i;
cord(p,2)=j;
p=p+1;
p=p+1;
end
end
end
Image Analyst
2017-3-3
编辑：Image Analyst
2017-3-3
mahesh, put this as an "Answer" below, not a comment up here. Also your entire code could be done in the single line
[rows, columns] = find(bwperim(img));
which is about the same at Nitin's accepted answer. However, neither that, nor your code will give the perimeter in a contiguous, connected way, like going clockwise around the region. It will give them on a column by column disconnected basis.
Cam S
2019-7-18
yes exactly! how do you do that image analyst
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更多回答（2 个）
Dishant Arora
2014-4-1
If you have a single blob the above answer would suffice but in case you have multiple objects use bwboundaries. It gives you the coordinates of boundary pixels.
doc bwboundaries
3 个评论
Milad
2014-4-1
Dishant Arora
2014-4-1
First one is the co-ordinates of boundary pixels and second is a labelled image. What output do you get from find()?? Post your code.
Image Analyst
2014-4-1
I agree with Dishant that bwboundaries is what you want , not bwperim followed by find. The difference in sizes between find and bwperim is probably due to bwboundaries "cutting corners" as it makes a 45 degree path while perim will give you all the rows and columns of the "L". Also find probably does not "follow the boundary" like bwboundaries does. With find you are not gauranteed that the pixel at the kth index is next to the pixel at the (k+1)st index since find probably goes in column major order like most things in MATLAB.
Arriana Nwodu
2018-8-13
0 个投票
So which code is correct? I tried all the ways listed and it didn't work
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