title: Is canny edge detection edge rotationlly invariant?
body: <p>Suppose that the Canny edge detector successfully detects an edge in an image. The edge is then rotated by θ, where the relationship between a point on the original edge <code>(x,y)(x,y)</code> and a point on the rotated edge  <code>(x′,y′)(x′,y′)</code>  is defined as <code>x′ = xcosθ; y′ = xsinθ;</code></p>
  
  <p>Will the rotated edge be detected using the same Canny edge detector? </p>
  
  <p><em>(I think we should find answer considering that the detection of an edge by the Canny edge detector depends only on the magnitude of its derivative.)</em></p>