From image array indices to position in projection plane (Mollweide).
- Input:
- if i and j are None, generate arrays of i and j as input
- i : if j is None, i[0], j[1] define array indices in Mollweide image.
- j : if defined, i,j define array indices in image.
- projinfo : additional projection information.
- Return:
- x,y : position in projection plane.