python读取二进制mnist实例详解
training data 数据结构：
<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
将整个文件读入：
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()下载本文