mmseg/datasets/transforms/loading.py中的LoadImageFromNpyFile函数不能适用npz格式的文件

[chizhiwei]

从741行开始，如下

    try:
        if Path(filename).suffix in ['.npy', '.npz']:
            img = np.load(filename)    # 问题：当读取的文件为npz格式时，包含了多项array数据，需要根据关键字进行指定
        else:
            if self.file_client_args is not None:
                file_client = fileio.FileClient.infer_client(
                    self.file_client_args, filename)
                img_bytes = file_client.get(filename)
            else:
                img_bytes = fileio.get(
                    filename, backend_args=self.backend_args)
            img = mmcv.imfrombytes(
                img_bytes,
                flag=self.color_type,
                backend=self.imdecode_backend)
    except Exception as e:
        if self.ignore_empty:
            return None
        else:
            raise e

    # in some cases, images are not read successfully, the img would be
    # `None`, refer to https://github.com/open-mmlab/mmpretrain/issues/1427
    assert img is not None, f'failed to load image: {filename}'
    if self.to_float32:
        img = img.astype(np.float32)

    results['img'] = img
    results['img_shape'] = img.shape[:2]   # 在这里会报出错误，因为此时的img变量是一个包含多项array的npz数据
    results['ori_shape'] = img.shape[:2]
    return results