OpenCvSharp function: CopyMakeBorder border extrapolation

CopyMakeBorder border extrapolation

Function description: Fill the border according to the specified border extrapolation method.

void CopyMakeBorder(InputArray src,
    OutputArray dst,
    int top,
    int bottom,
    int left,
    int right,
    BorderTypes borderType,
    Scalar? value = null)

parameter	illustrate
InputArray src	source image
OutputArray dst	output image
int top	Upper bound extrapolated pixels
int bottom	Lower bound extrapolated pixels
int left	left border extrapolated pixels
int right	Right border extrapolated pixels
BorderTypes borderType	Boundary Extrapolation Type
Scalar? value	When the extrapolation type is Constant, the padding value

BorderTypes values

value	illustrate
Constant	Fill with fixed value `iiiiii|abcdefgh|iiiiiii` with some specified `i`
Replicate	Repeat filling by boundary value `aaaaaa|abcdefgh|hhhhhhh`
Reflect	Reflection/mirror fill (starting from boundary pixels) `fedcba|abcdefgh|hgfedcb`
Wrap	Fill by opposite image pixels `cdefgh|abcdefgh|abcdefg`
Reflect101	Mirror fill (starting one pixel inward from the border) `gfedcb|abcdefgh|gfedcba`
Transparent	CopyMakeBorder function is not supported `uvwxyz|absdefgh|ijklmno`
Default	Same as Reflect101
Isolated	Do not fill based on the original image Same as Constant?

Fill example

Constant fills with fixed value

 Replicate repeats filling by boundary pixels

 Reflect reflection/mirror fill

Wrap fills the image pixels on the opposite side

 Reflect101 mirror fill (starting 1 pixel inward from the border)

Isolated does not fill based on the original image

 Source code example

private void TestBorderTypes(Mat src) {
    var bBorderTypes = Enum.GetValues(typeof(BorderTypes));
    foreach(BorderTypes b in bBorderTypes) {
        try {
            //外推宽度
            var extend = 100;
            using var dst = new Mat();
            Cv2.CopyMakeBorder(src, dst, extend, extend, extend, extend, b, Scalar.All(127));
            Cv2.Rectangle(dst, new Rect(extend, extend, src.Width, src.Height), Scalar.Red);
            Cv2.ImShow($"{b.ToString()}", dst);                    
        }
        catch (Exception ex) {
            //不支持 Transparent
        }
    }
    Cv2.WaitKey();
    Cv2.DestroyAllWindows();
}

OpenCvSharp function examples (Table of Contents)