how to find convex hull and the area of intersection

Hello,

I want to find the convex hull of this two triangle and then find the intersection area of them.to find convex hull i tried convhull(A,B) but it did not work. Is there anybody to explain how can i use convhull function for the code below.

P(1,:) = [0.9 2.1]; P(2,:) = [2.8 5.2]; P(3,:) = [5.7 2.3];

Q(:,:) = ... [2.7 1.1 5.6 4.1 8.0 1.8];

X = [P(:,1) P(1,1)];

Y = [P(:,2) P(1,2)];

 line(X,Y)

 A = [Q(:,1)
    Q(1,1)];

B = [Q(:,2) Q(1,2)];

 line(A,B)

Answer 1

[Image Analyst]

Sum the intersection image to find the area. Try this code:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures.
clear;  % Erase all existing variables.
workspace;  % Make sure the workspace panel is showing.
fontSize = 20;

P(1,:) = [0.9 2.1]; 
P(2,:) = [2.8 5.2]; 
P(3,:) = [5.7 2.3];

windowSize = 30;

image1 = poly2mask(P(:,1), P(:,2), windowSize, windowSize);
subplot(2, 2,1);
imshow(image1);
title('P', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]); % Maximize figure.
set(gcf,'name','Demo by ImageAnalyst','numbertitle','off') 

Q = [2.7 1.1; 5.6 4.1; 8.0 1.8];
image2 = poly2mask(Q(:,1), Q(:,2), windowSize, windowSize);
subplot(2, 2, 2);
imshow(image2);
title('Q', 'FontSize', fontSize);

intersectionImage = image1 | image2;
subplot(2, 2, 3);
imshow(intersectionImage);
title('Intersection Image', 'FontSize', fontSize);

intersectionCoords = [P;Q];
convexHullIndex = convhull(intersectionCoords)

convexHullImage = poly2mask(intersectionCoords(convexHullIndex,1), intersectionCoords(convexHullIndex,2), windowSize, windowSize);
subplot(2, 2, 4);
imshow(convexHullImage);
title('Convex Hull Image', 'FontSize', fontSize);

[dediydi]

thanks a lot for your attention, but that is not what i really want. i want to see the two triangle,their convex hull and intersection points on the standart output. Maybe we should not use poly2mask function.

[Image Analyst]

If you don't want to do it quantized (via digital arrays/images) then you're going to have to figure it out analytically using formulas for the 6 lines to find intersection points and the overlap area. Maybe the Symbolic Toolbox could help you - I don't know because I don't have that toolbox.