Measurement of the Area for Different images

I made four different shapes:
1. Square
2. Circle
3. Triangle
4. Irregular shape


Using scilab, I made a program to get the area for each of the shapes I made. I posted the source code below:






a = imread("C:\Documents and Settings\AP186user15\Desktop\ryt.bmp");//command line for opening image file
b= im2bw(a,1);
[x,y] = follow(b);
c = size(x);
d = size(y);
c1 = c(1);
d1 = d(1);
x_1 = x;
y_1 = y;

x_1(2:c1) = x(1:c1-1);
x_1(1) = x(d1);
y_1(2:d1) = y(1:d1-1);
y_1(1) = y(d1);
initial = x.*y_1 - y.*x_1;
area = (0.5*(sum(initial)));
absolute_area = (area^2)^0.5;
//Getting the percent error //
Error = ((sum(b)-absolute_area)/sum(b))*100;


The resulting areas and the actual area:

	Area	Pixel Count Area	Percent Error
Square	88209	88804	0.67
Circle	71552	71981	0.6
Triangle	44999.5	45450	0.99
Irregular Shape	48780	49383	1.22

For this program, Ed helped me in identifying errors in my program and Raf helped me understand the equation I used in obtaining the area of the image.

For this activity, I will give myself a grade of 9.5 / 10. It's not 10 because others helped me do this program.