Filling holes inside a binary object

Question

I have a problem with filling white holes inside a black coin so that I can have only 0-255 binary images with filled black coins. I have used a Median filter to accomplish it but in that case connection bridge between coins grows and it goes impossible to recognize them after several times of erosion... So I need a simple `floodFill` like method in opencv Here is my image with holes: EDIT: `floodfill` like function must fill holes in big components without prompting X, Y coordinates as a seed... EDIT: I tried to use the `cvDrawContours` function but it doesn't fill contours inside bigger ones. Here is my code: ``` CvMemStorage mem = cvCreateMemStorage(0); CvSeq contours = new CvSeq(); CvSeq ptr = new CvSeq(); int sizeofCvContour = Loader.sizeof(CvContour.class); cvThreshold(gray, gray, 150, 255, CV_THRESH_BINARY_INV); int numOfContours = cvFindContours(gray, mem, contours, sizeofCvContour, CV_RETR_CCOMP, CV_CHAIN_APPROX_SIMPLE); System.out.println("The num of contours: "+numOfContour…

Accepted Answer

There are two methods to do this:

1) Contour Filling:

First, invert the image, find contours in the image, fill it with black and invert back.

```
des = cv2.bitwise_not(gray)
contour,hier = cv2.findContours(des,cv2.RETR_CCOMP,cv2.CHAIN_APPROX_SIMPLE)

for cnt in contour:
    cv2.drawContours(des,[cnt],0,255,-1)

gray = cv2.bitwise_not(des)
```

Resulting image:

2) Image Opening:

```
kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE,(3,3))
res = cv2.morphologyEx(gray,cv2.MORPH_OPEN,kernel)
```

The resulting image is as follows:

You can see, there is not much difference in both cases.

NB: gray - grayscale image, All codes are in OpenCV-Python

Reference. OpenCV Morphological Transformations

Filling holes inside a binary object

Solution

Problem