Figure 17

Filter transformation description [39]. The original system of axes is represented by x and y, and the ellipse system of axes by u and v. ϕ represents the angle of the second axis of the non-orthogonal basis. The integration domain of a pixel is limited by four lines of equations: \(x = i\delta \), \(x = (i+1)\delta \), \(y = j\delta \) and \(y = (j+1)\delta \). Rewriting these fours equations in the new system of axes through a coordinate change enables us to write Eq. (61)