CODEWITHSUNDEEP
c++imageopencv
Alan
Alan

Reputation: 121

Remove black Background from an image.

I'm new to image processing and development. I have used opencv, There I need to extract circle from a given image. That circle given x, y coordinates are (radius) in Oder to do that I used following code. But my problem is I have to take black rectangle. So the image patch having unwanted black pixels. How do I save just only circle?

my code

double save_key_points(Mat3b img, double x, double y, double radius, string 

    filename, string foldername)
    {

        // print image height and width first and check.
        Vec3f circ(x, y, radius);

// Draw the mask: white circle on black background
Mat1b mask(img.size(), uchar(0));

circle(mask, Point(circ[0], circ[1]), circ[2], Scalar(255), CV_FILLED);


// Compute the bounding box
Rect bbox(circ[0] - circ[2], circ[1] - circ[2], 2 * circ[2], 2 * circ[2]);

// Create a black image
Mat3b res(img.size(), Vec3b(0, 0, 0));

// Copy only the image under the white circle to black image
img.copyTo(res, mask);

// Crop according to the roi
res = res(bbox);

//remove black but doesn't work.
Mat tmp, alpha;
threshold(res, alpha, 100, 255, THRESH_BINARY);
        // Save the image
        string path = "C:\\Users\\bb\\Desktop\\test_results\\test_case8\\" + foldername + filename + ".png";

        imwrite(path, res);
        Mat keypointimg = imread(path, CV_LOAD_IMAGE_GRAYSCALE);

        //print the cordinate of one patch.
        cordinate_print(keypointimg, radius);

    }

(Here i want without black background) Out put Patch

Upvotes: 1

Views: 730

Answers (1)

C.Radford
C.Radford

Reputation: 932

If I understand what you are asking correctly you could remove the black from an image you can use a mask. The mask can highlight anything that is of a certain colour or in your case the shade of black. Check out the link for this implementation and see if it is what you are looknig for. It is in python but can be easily adapted.

Image Filtering

Upvotes: 1

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