How to draw polygon having set of unordered points?

How to draw polygon having set of unordered points in binary image.I want approximately all the points to be connected in the polygon which function would help?

Answer 1

[Image Analyst]

There are multiple polygons that could be drawn this way. You must describe some algorithm for how to order them, such as the angle to the next point must always be clockwise (or counterclockwise) or something like that. You could find the centroid (average of x and y) then calculate angles of all points, and then sort based on angles. Is that what you want to do?

Here's some untested code:

meanx = mean(x);
meany = mean(y);
angles = atan( (y-ymean) ./ (x-xmean));
[sortedAngles, sortIndices] = sort(angles);
reorderedx = x(sortIndices);
reorderedy = y(sortIndices);
plot(reorderedx, reorderedy, 'bo-');

[Abinaya]

thank you. I ll try this.

[Image Analyst]

Try this:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures if you have the Image Processing Toolbox.
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 22;
x = rand(15,1);
y = rand(15,1);
subplot(1,2,1);
plot(x, y, 'rs-', 'LineWidth', 2);
grid on;
title('Random Points', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off') 

meanx = mean(x);
meany = mean(y);
angles = atan2( (y-meany),(x-meanx))
[sortedAngles, sortIndices] = sort(angles);
reorderedx = x(sortIndices);
reorderedy = y(sortIndices);
subplot(1,2,2);
plot(meanx, meany, 'g+', 'MarkerSize', 15);
hold on;
plot(reorderedx, reorderedy, 'bo-', 'LineWidth', 2);
grid on;
title('Sorted by Angle', 'FontSize', fontSize);

[Ahmed Hossam]

concave polygons?

[Image Analyst]

Ahmed, what does your comment mean?

[Wen Fang]

Great answer! What if the random points become 3D points?

[Wen Fang]

@Image Analyst

[Image Analyst]

Try delaunayn()

T = delaunayn(X) computes a set of simplices such that no data points of X are contained in any circumspheres of the simplices. The set of simplices forms the Delaunay triangulation. X is an m-by-n array representing m points in n-dimensional space. T is a numt-by-(n+1) array where each row contains the indices into X of the vertices of the corresponding simplex.