Removing blobs from a binary image

Question

I have a binary image which contain few blobs.

I want to remove blobs which are less than a certain area.

Can any one suggest me a way?

I am using Open-C

Answer 1

You can do something like this:

// your input binary image
// assuming that blob pixels have positive values, zero otherwise
Mat binary_image; 

// threashold specifying minimum area of a blob
double threshold = 100;

vector> contours;
vector hierarchy;
vector small_blobs;
double contour_area;
Mat temp_image;

// find all contours in the binary image
binary_image.copyTo(temp_image);
findContours(temp_image, contours, hierarchy, CV_RETR_CCOMP,
                                                  CV_CHAIN_APPROX_SIMPLE);

// Find indices of contours whose area is less than `threshold` 
if ( !contours_all.empty()) {
    for (size_t i=0; i