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To produce a max output from an image

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Tze Huey Tam 2018-10-8

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评论： Walter Roberson 2018-10-8

Hi all,

I have a image with 4577x4088 dimension. However, I applied this formula: B(x) = max (Mk(x)) to image, the output I get is in image but dimension became 1x4088. So, how could I remain the 4577x4088 dimension after apply the formula?

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KSSV 2018-10-8

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If you pick max from the matrix..there exists only one maximum value..how you are expecting the same dimension again?

Guillaume 2018-10-8

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编辑：Guillaume 2018-10-8

In addition to what KSSV said,

I applied this formula: B(x) = max (Mk(x))

We have no idea what B, x, Mk are. I suspect that Mk is your image but we certainly have no idea what x is. If x is scalar, then the maximum of a single value is itself and the whole thing is a waste of time.

Tze Huey Tam 2018-10-8

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x is the value of each pixel

Walter Roberson 2018-10-8

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And what is Mk?

Tze Huey Tam 2018-10-8

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编辑：Walter Roberson 2018-10-8

Mk indicates the spectral value of pixel x at band k

Kevin Chng 2018-10-8

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Or you may elaborate further what do you want to achieve?

Tze Huey Tam 2018-10-8

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I want to apply Morphological Building Index to image. The first step of this index is to get the maximum value of image.. For more details about this index, please referred to this paper "A Multidirectional and Multiscale Morphological Index for Automatic Building Extraction from Multispectral GeoEye-1 Imagery"

Walter Roberson 2018-10-8

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Unless Mk returns multiple values for every input pixel, then the size of the result of Mk is no bigger than the size of the image. When you apply single input max() to something no bigger than the image, you are going to get a result that is smaller than the image.

There is a two input version of max() as well. max(A, B) is the location by location maximum of the two corresponding locations in the two arrays, and the size of the result is the size of the input array.

For example it is valid to max(A,0) which is equivalent to replacing every negative value in A with 0.

But when there is only one input then the output of max is to take the maximum along the first nonscalar dimension. In your case that would be the maximum of each column.

Tze Huey Tam 2018-10-8