why different answers with roipoly and polyarea

clear all close all

nrows=300; ncols=400; N=4; % number of vertices

ang=0:360/N:360; ang=ang+45; radius=min(nrows,ncols)/2; h=ncols/2+radius*cosd(ang); v=nrows/2+radius*sind(ang);

im=zeros(nrows,ncols); im=roipoly(im,h,v); area=sum(sum(im)) area2=polyarea(h,v)

Answer 1

[Sachin Ganjare]

'roipoly' is used to get manually the region of interest

'polyarea' is used to calculate the ROI area

Example:

% imshow first, then:

[x, y, BW, xi, yi] = roipoly;

area = polyarea(xi,yi);

Hope it helps!!!