Load pre-processed depth for NYUDv2 segmentation set.

def load_depth(self, idx):
        """
        Load pre-processed depth for NYUDv2 segmentation set.
        """
        im = Image.open('{}/data/depth/img_{}.png'.format(self.nyud_dir, idx))
        d = np.array(im, dtype=np.float32)
        d = np.log(d)
        d -= self.mean_logd
        d = d[np.newaxis, ...]
        return d