Identitify the center of the Image correspond to one coordinate.

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