python如何读取二进制mnist实例详解

<br>[offset] [type] [value] [description]
0000 32 bit integer 0x00000803(2051) magic number
0004 32 bit integer 60000 number of images
0008 32 bit integer 28 number of rows
0012 32 bit integer 28 number of columns
0016 unsigned byte ?? pixel
0017 unsigned byte ?? pixel
........
xxxx unsigned byte ?? pixel

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

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

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()