How can i write this equation in matlab ??????

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Mary Jon 2013-9-18

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(v(i,j))^(k+1)= (1-ω)(v(i,j))^(k)-ω[(W1(i,j)(v(i+1,j))^(k)+ W2(i,j)(v(i-1,j))^(k+1)+ W3(i,j)(v(i,j+1)^(k)+ W4(i,j)(v(i,j-1))^(k+1)(/(W i,j)]

v matrix k iteration W may by matrix (have i &j) w constant

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Answer 1

John Petersen 2013-9-18

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在 MATLAB Online 中打开

The trick is to update v(i-1,j) and v(i,j-1) without updating v(i+1,j) and v(i,j+1) before going on the v(i,j). After that do:

v(i,j)= (1-ω)*v(i,j) - ω*[(W1(i,j)*v(i+1,j) + W2(i,j)*v(i-1,j) + W3(i,j)*v(i,j+1) + W4(i,j)*v(i,j-1))/W(i,j)]

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Image Analyst 2013-9-18

convolution, conv2(), and imfilter() do this "trick" inherently and efficiently. With your code, as you move over to the next j, your v(i,j) will now be the new v(i, j-1) and will be affected. So it will have some kind of recursive/hysteresis effect or trailing blur or something that's not right. imfilter() and conv2() do not suffer from this. If she insists on using two nested for loops (a much less efficient approach especially for larger windows) then she'll have to at least assign the result (right hand side of the equation) to a new output variable, like vout(i,j), not the original input variable.

conv2() and imfilter are more efficient because they only need to read in and discard a few of the pixels on the edge, not the whole array. For example with a 7x7 window, you have 49 elements/pixels in the window but as you slide over one pixel you only need to read in 7 new pixels, not all 49.

Mary Jon 2013-9-21

I do conv2(), and imfilter() ,but no result getting yet ,where is wrong?

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Answer 2

Image Analyst 2013-9-18

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https://ww2.mathworks.cn/matlabcentral/answers/87603-how-can-i-write-this-equation-in-matlab#answer_97167

编辑：Image Analyst 2013-9-18

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Looks like unsharp masking, so you can do this

kernel = [0, W1, 0; W3, 0, W4; 0, W2, 0];
filtered = conv2(vk, kernel, 'same');
vk = (1-omega)*vk + filtered./W;

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Image Analyst 2013-9-20

Just tell me what it's supposed to do. It looks like you might be able to use convolution but if W1, etc. are not constants, then maybe not. I really need to know what the intent of that code is. For example if it's to do unsharp masking then you should use a different output variable if you're going to do it in a loop so that you avoid hysteresis. I suspect that you transcribed the equation incorrectly but I can't say exactly how to fix it unless I know what you want to accomplish. John's code will probably work in that it will do what you tried to do, but I'm not sure that is really what you want to do because I don't feel that you described in words properly what you want to do.

Mary Jon 2013-9-20