How To Remove Border Components In Python 2.7 Using Opencv

I want to remove the components which are touching the border of the image. I'm using OpenCV 2.4.10 and Python 2.7. I have done HSV conversion and THRESHOLD_BINARY of the image, n

Solution 1:

There is no direct method in openCV to do that. You can write a function using the method floodFill and loop over for border pixels as seed points.

floodFill(dstImg,seed,Scalar (0));

where:

dstImg : Output with border removed.

seed : [(x,y) points] All the border co-ordinates

Scalar(0) : The color to be filled if a connected region towards a seed point is found. Hence (0) as your case is to fill it as black.

Sample:

int totalRows = srcImg.rows;
int totalCols = srcImg.cols;
int strt = 0, flg = 0;
int iRows = 0, jCols = 0;
while (iRows < srcImg.rows)
{
    if (flg ==1)
        totalRows = -1;
    Point seed(strt,iRows);     
    iRows++;
    floodFill(dstImg,seed,Scalar (0));
    if (iRows == totalRows)
    {
        flg++;
        iRows = 0;
        strt = totalCols - 1;
    }
}       

Similarly do modify it for columns. Hope It helps.

Solution 2:

Not very elegant, but you could enclose each contour in a bounding rectangle and test whether the coordinates of this rectangle fall on or outside the boundary of the image (im)

for c in contours:
    include = True  
    # omit this contour if it touches the edge of the image
    x,y,w,h = cv2.boundingRect(c)       
    if x <= 1 or y <=1:
        include = False                 
    if x+w+1 >= im.shape[1] or y+h+1 >= im.shape[0]:
        include = False
    # draw the contour
    if include == True:
        cv2.drawContours(im, [c], -1, (255, 0, 255), 2)