How to find the boundary pixel values round by round ?

consider the two images below

The first image shows a damaged area of a image. By using the below code the boundary pixel values' co-ordinations can be found. Then I need to find the pixels of the inner rounds of the ROI's boundary one by one as mentioned in the second image in black again and again. How can I easily do that ?

rgbImage = imread('image.png');

redChannel = rgbImage(:, :, 1);
ZeroPlate = redChannel == 0;

for j = 1 : numberOfDamagedRegions

thisBoundary = boundaries{j};
    x = thisBoundary(:, 1);
    y = thisBoundary(:, 2);

  for index  = 1 : length(x)
          row    = x(index);
          column = y(index);
    ZeroPlate(row, column)=true;
  end

end