python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  "htmlcode">

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



读取头四个32bit的interger:


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



读取一个图片，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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