CODEWITHSUNDEEP
c++opencv
xuhdev
xuhdev

Reputation: 9333

Gaussian Blurring in OpenCV: set 0 constant outside the border?

I'm using the GaussianBlur function in OpenCV to perform Gaussian blurring. While the bordertype parameter can be filled with BORDER_CONSTANT, it doesn't allow to set the value of the constant. From the explanation of borderInterpolate, it seems that the value of the constant is set to -1. Is it possible to set it to 0?

Thanks!

Upvotes: 2

Views: 3323

Answers (2)

Bull
Bull

Reputation: 11941

The reason borderInterpolate returns -1 for BORDER_CONSTANT is so this code in filter.cpp works:

        int srcY = borderInterpolate(dstY + dy + i + roi.y - ay,
                        wholeSize.height, columnBorderType);
        if( srcY < 0 ) // can happen only with constant border type
            brows[i] = alignPtr(&constBorderRow[0], VEC_ALIGN);

That is, it causes your border to be set to zero, which is what you want. The border is not being set to -1.

Upvotes: 1

Radford Parker
Radford Parker

Reputation: 731

I think that the -1 is the return value for the function borderInterpolate() when you use BORDER_CONSTANT. Check out the top section of this page:

http://docs.opencv.org/modules/imgproc/doc/filtering.html?highlight=gaussianblur#image-filtering

"all the non-existing pixels are zeros (“constant border” extrapolation method)", so it does already use zeros for the GaussianBlur function.

Upvotes: 3

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