docs: def _map_center(self, coord, val):
          ''' Identitify the center of the Image correspond to one coordinate. '''
  
          if self.ppd in [4, 16, 64, 128]:
              res = {'lat': 0, 'long': 360}
              return res[coord] / 2.0
          elif self.ppd in [256]:
              res = {'lat': 90, 'long': 180}
              c = (val // res[coord] + 1) * res[coord]
              return c - res[coord], c
          elif self.ppd in [512]:
              res = {'lat': 45, 'long': 90}
              c = (val // res[coord] + 1) * res[coord]
              return c - res[coord], c
          elif self.ppd in [1024]:
              res = {'lat': 15, 'long': 30}
              c = (val // res[coord] + 1) * res[coord]
              return c - res[coord], c