code: def load_hha(self, idx):
          
          im = Image.open('{}/data/hha/img_{}.png'.format(self.nyud_dir, idx))
          hha = np.array(im, dtype=np.float32)
          hha -= self.mean_hha
          hha = hha.transpose((2,0,1))
          return hha
docs: Load HHA features from Gupta et al. ECCV14.
          See https://github.com/s-gupta/rcnn-depth/blob/master/rcnn/saveHHA.m