How to find the coordinates ( x-axis and y-axis) of the white square

Answer 1

[Cris LaPierre]

Just the x and y coordinate of every white pixel?

img=imread('image.jpeg');
imshow(img)
[m,n] = find(img==255);

If you want to verify, do something like this. For an image, rows are on the Y axis, colums on the x

hold on
plot(n,m,'g.')

If you actually want the perimeter, that's a little tougher, but perhaps this can get you started?