v is the eigenvector of the tensor with the highest eigenvalue, and has a unit norm by construction. Then v[0] is the x coordinate of v, v[1] is the y coordinate, ... In our code we use values between 0 and 1 for the r, g, and b color ranges so we don't need any rescaling of these values since v is of unit norm. However if you want r, g, b to be in between 0 and 255 you would need to resale by 255 of course.