Color in white only pixels defined by a matrix [rx2]

Hi! I would like to keep white pixels only at the desired coordinates ("contour") while transforming other pixels with black color. Is there an easy way to be able to do this?

BW = imread('blobs.png');
imshow(BW)
r1 = 163;
c1 = 37;
contour = bwtraceboundary(BW,[r1 c1],'W');
hold on
plot(contour(:,2),contour(:,1),'g','LineWidth',2)

Answer 1

[Voss]

BW = imread('blobs.png');
imshow(BW)
r1 = 163;
c1 = 37;
contour = bwtraceboundary(BW,[r1 c1],'W');
hold on
plot(contour(:,2),contour(:,1),'g','LineWidth',2)

figure
BW_new = BW;                                                % make a copy of BW
BW_new(:) = 0;                                              % set all pixels to black
BW_new(sub2ind(size(BW),contour(:,1),contour(:,2))) = 1;    % set "contour" pixels to white
imshow(BW_new)