After Canny, those blobs are single pixel wide blobs, so it makes no sense to call bwboundaries() on them. That would just simply give you the same coordinates you already have, any maybe even doubled up as it goes to one end and back again. I think you want to use regionprops and ask for PixelList.
rgbImage = imread('DJI_0022.jpg'); %inputs image
hFig = figure;
subplot(2, 2, 1);
imshow(rgbImage)
axis('on', 'image');
impixelinfo;
title('Original RGB Image', 'FontSize', 20);
grayImage = rgb2gray(rgbImage); %convers to grayscale
subplot(2, 2, 2);
imshow(grayImage)
axis('on', 'image');
impixelinfo;
title('Gray Scale Image', 'FontSize', 20);
edgeImage = edge(grayImage, 'Canny', 0.6);
subplot(2, 2, 3);
imshow(edgeImage)
axis('on', 'image');
title('Canny Edge Image', 'FontSize', 20);
hFig.WindowState = 'maximized';
drawnow;
% Get coordinates.
props = regionprops(edgeImage, 'PixelList');
for k = 1 : length(props)
thisList = props(k).PixelList;
fprintf('\nFor blob #%d of %d:\n ', k, length(props))
for k2 = 1 : size(thisList, 1)
thisx = thisList(k2, 1);
thisy = thisList(k2, 2);
fprintf('(%d, %d), ', thisx, thisy);
end
end
