how to clear the border of matrix?

Question

Tan Wen Kun 2015-12-4

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评论： Tan Wen Kun 2015-12-4

I have a label image matrix

img=
1 1 2 2 2 3 3 3 3
2 2 2 9 3 3 3 3 3
1 9 9 9 9 9 9 3 3
8 8 8 8 8 8 8 8 3
8 8 8 7 7 7 7 7 3
7 7 7 7 1 1 7 7 3
1 1 1 1 1 1 1 1 1

I want to clear the side border and register it and clear the inside matrix with the value is same as side so turn them into 0.

side=
        1 1 1 2 2 2 3 3 3 3
        1                 3
        1                 3
        1                 3
        1                 3
        1                 3
        1 1 1 1 1 1 1 1 1 1

side =(1,2,3)

result=
0 0 0 0 0 0 0 0 0
0 0 0 9 0 0 0 0 0
0 9 9 9 9 9 9 0 0
8 8 8 8 8 8 8 8 0
8 8 8 7 7 7 7 7 0
7 7 7 7 0 0 7 7 0
0 0 0 0 0 0 0 0 0

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Answer 1

Guillaume 2015-12-4

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编辑：Guillaume 2015-12-4

在 MATLAB Online 中打开

It's actually very simple using set operations:

 img = [1 1 1 2 2 2 3 3 3 3
        1 2 2 2 9 3 3 3 3 3
        1 1 9 9 9 9 9 9 3 3
        1 8 8 8 8 8 8 8 8 3
        1 8 8 8 7 7 7 7 7 3
        1 7 7 7 7 1 1 7 7 3
        1 1 1 1 1 1 1 1 1 1];
result = img;
result(ismember(result, union(result(:, [1 end]), result([1 end], :)))) = 0

union gives you the unique labels that are part of the vertical and horizontal borders. ismember tells you which labels at what position are parts of that union. You then use the logical vector generated by ismember to set the respective labels to 0.

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Answer 2

Image Analyst 2015-12-4

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在 MATLAB Online 中打开

If you want, you can just set the rows and columns to zero

   img = [1 1 1 2 2 2 3 3 3 3
          1 2 2 2 9 3 3 3 3 3
          1 1 9 9 9 9 9 9 3 3
          1 8 8 8 8 8 8 8 8 3
          1 8 8 8 7 7 7 7 7 3
          1 7 7 7 7 1 1 7 7 3
          1 1 1 1 1 1 1 1 1 1];
result = img;
result(1,:)=0;
result(end,:)=0;
result(:,1)=0;
result(:,end)=0

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Image Analyst 2015-12-4

I don't understand any of what you said. But whatever . . . you've accepted Guillaume's answer so I guess your problem is resolved now and that's what counts. Good luck.

Tan Wen Kun 2015-12-4

Because I doing some dumb image segmentation so sometime my question is look abit foolish~my lecturer just give me the step that whatever now me can do in time so my work is abnormal than normal image segmentation

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