code: def distance_to_edge(geom, skydir):
      
  
      # FIXME: We should add a pixel_size property in gammapy.maps
      # FIXME: We should make this into a MapGeom method 
      
      xpix, ypix = skydir.to_pixel(geom.wcs, origin=0)
      deltax = np.array((xpix - geom.center_pix[0]) * geom._cdelt[0],
                        ndmin=1)
      deltay = np.array((ypix - geom.center_pix[1]) * geom._cdelt[1],
                        ndmin=1)
  
      deltax = np.abs(deltax) - 0.5 * geom.width[0]
      deltay = np.abs(deltay) - 0.5 * geom.width[1]
  
      m0 = (deltax < 0) & (deltay < 0)
      m1 = (deltax > 0) & (deltay < 0)
      m2 = (deltax < 0) & (deltay > 0)
      m3 = (deltax > 0) & (deltay > 0)
      mx = np.abs(deltax) <= np.abs(deltay)
      my = np.abs(deltay) < np.abs(deltax)
  
      delta = np.zeros(len(deltax))
      delta[(m0 & mx) | (m3 & my) | m1] = deltax[(m0 & mx) | (m3 & my) | m1]
      delta[(m0 & my) | (m3 & mx) | m2] = deltay[(m0 & my) | (m3 & mx) | m2]
      return delta
docs: Return the angular distance from the given direction and
      the edge of the projection.