How connect the coordinate and fill the area to create a binary mask?

I need to create a binary mask from the series of coordinate. My current code is like below but what it does, the edges of the mask are not smooth. I think it is not precise and I need to make sure I am connecting exact coordinate and connect them together.

Here on the left side I plotted the points (always is 42 points) and on the right side is the output of the code. As you can see the edges are not smooth.

Here is the current code and the output:

im is image with size of 112 * 112 that filled with all zero values except coordinates and inside the region filled with the 255.

function BW = mask_data(X,Y, im)

X = round(X);
Y = round(Y);

%round coordinates
X ( X < 1 ) = 1;
Y ( Y < 1 ) = 1;

BW = im > 255;
for p = 1:length(X)
    
    BW(Y(p),X(p)) = 1;
end

BW = BW * 255;
BW = bwconvhull(BW);
BW = im2uint8(BW);
figure;
imshow(BW);
close all;


end

[KSSV]

Try boundary.

[Neda]

can you please provide more details. How can I get the boundry for all the points, and what is the next action after that.

Answer 1

[darova]

• use edge to detect edge pixels
• use find to find all coordinates
• use boundary to calculate correct order

Answer 2

[Image Analyst]

Use poly2mask():

BW = poly2mask(X, Y, size(im, 1), size(im, 2));

It will draw a straight line between each pair of points in X and Y.

If you need something even smoother, you can use splines to smooth the boundary of BW while still going through the X and Y points by creating additional points in between your knot points using cubic polynomical. See attached demos.