Finding vertices of a polygon binary mask

Hi, all. I have a question on finding the vertices of a polygon binary mask. I want to obtain the x,y coordinates of the polygon. However, my code doesn't work. is there any problem?

if true
mask = createMask(h);
structBoundaries = bwboundaries(mask);
xy=structBoundaries{1}; % Get n by 2 array of x,y coordinates.
x = xy(:, 2); % Columns.
y = xy(:, 1); % Rows
[topLine, indice1] = min(x);
x1 = topLine;
y1 = y(indice1);
[bottomLine, indice2] = max(x);
x2 = bottomLine;
y2 = y(indice2);
[leftColumn, indice3] = min(y);
x3 = x(indice3);
y3 = leftColumn;
[rightColumn, indice4] = max(y);
x4 = x(indice4);
y4 = rightColumn;
width = bottomLine - topLine + 1;
height = rightColumn - leftColumn + 1;
polygon = int32([x1 y1 x2 y2 x3 y3 x4 y4])
end

Answer 1

[Image Analyst]

x is not line. y is not column. You got it reversed - a very common mistake. (x,y) IS NOT the same as (row, column). You need to say y1 = topLine, not x1=topLine. So swap x and y and it should be fine, though you really only need x1,x2,y1,y2 not all the way up to 4 each of them.