mnist.py 文件源码

def _extract_images(filename):
        """???????????????????

        :param filename: ?????
        :return: 4??numpy??[index, y, x, depth]? ???np.float32
        """
        images = []
        print('Extracting {}'.format(filename))
        with gzip.GzipFile(fileobj=open(filename, 'rb')) as f:
            buf = f.read()
            index = 0
            magic, num_images, rows, cols = struct.unpack_from('>IIII', buf, index)
            if magic != 2051:
                raise ValueError('Invalid magic number {} in MNIST image file: {}'.format(magic, filename))
            index += struct.calcsize('>IIII')
            for i in range(num_images):
                img = struct.unpack_from('>784B', buf, index)
                index += struct.calcsize('>784B')
                img = np.array(img, dtype=np.float32)
                # ????[0,255]???[0,1]
                img = np.multiply(img, 1.0 / 255.0)
                img = img.reshape(rows, cols, 1)
                images.append(img)
        return np.array(images, dtype=np.float32)