Replacing centre pixel value

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FIR 2012-12-19

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https://ww2.mathworks.cn/matlabcentral/answers/56970-replacing-centre-pixel-value

        I have a code ,of 7x7 natrix in that for each 3x3 i have found minimum value and if that minimum value is greater the centre pixel value ,the centre pixel value must be replaced by 5.have problem in replacing centre pixel value ,please help
for i=2:6
    for j=2:6
        K= A(i-1:i+1,j-1:j+1);
        T=K(2,2);finding centre pixel value
          B=min(K(:));
          if B>T
              %%%please tell what must come here replacing centre pixel vaue by 5
              %%%%I DID   K(2,2)=5;
          else
              %%%%%%%%%here also
              %%I DID K=K;
          end
      end
  end
BUT I GET 3x3 matrix only,how to get 7x7 matrix
please assist
        please assist

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Image Analyst 2012-12-19

You've been posting here long enough that you should already know how to format your questions. Please review the tutorial http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup. By the way, you can type Ctrl-A, Ctrl-I, Ctrl-C when your code is in MATLAB to fix indenting problems. Then come here and paste it in, highlight it, and click {}Code. Do not have any spaces before non-code text (like your first paragraph). It's not hard - give it a try.

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回答（2 个）

Image Analyst 2012-12-19

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/56970-replacing-centre-pixel-value#answer_68934

The minimum value in a 7x7 window will never be greater than the center value. Please explain what you are thinking.

By the way, you can call imerode() to get the local min values in a 7x7 sliding window.

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Image Analyst 2012-12-19

编辑：Image Analyst 2012-12-19

But the concept is flawed! Anyway, you might play around and use imerode and subtract it from your original, or vice-versa. Then threshold and replace items meeting the threshold with 5. I think you already know how to do that without loops. Even if you did want to use loops, you'd have to have 4 loops, not 2. Two to scan rows and columns, and then at each pixel, another two loops (like you already have) to scan a window around that pixel. But not a very efficient way to do it. I suggest you review the code examples I gave you in your prior, related questions.

FIR 2012-12-20