python讀取二進制mnist實例詳解

training data 數據結構：

<br>[offset] [type]     [value]     [description]0000   32 bit integer 0x00000803(2051) magic number0004   32 bit integer 60000      number of images0008   32 bit integer 28        number of rows0012   32 bit integer 28        number of columns0016   unsigned byte  ??        pixel0017   unsigned byte  ??        pixel........xxxx   unsigned byte  ??        pixel 

  將整個文件讀入：

filename = 'train-images.idx3-ubyte'binfile = open(filename , 'rb')buf = binfile.read()

讀取頭四個32bit的interger:

index = 0magic, numImages , numRows , numColumns = struct.unpack_from('>IIII' , buf , index)index += struct.calcsize('>IIII')

讀取一個圖片，784=28*28 ：

im = struct.unpack_from('>784B' ,buf, index)index += struct.calcsize('>784B') im = np.array(im)im = im.reshape(28,28) fig = plt.figure()plotwindow = fig.add_subplot(111)plt.imshow(im , cmap='gray')plt.show()

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