mnist数据集下载

http://yann.lecun.com/exdb/mnist/

THE MNIST DATABASE

of handwritten digitsYann LeCun, Courant Institute, NYUCorinna Cortes, Google Labs, New YorkChristopher J.C. Burges, Microsoft Research, Redmond

The MNIST database of handwritten digits, available from this page, has a training set of 60,000 examples, and a test set of 10,000 examples. It is a subset of a larger set available from NIST. The digits have been size-normalized and centered in a fixed-size image.

It is a good database for people who want to try learning techniques and pattern recognition methods on real-world data while spending minimal efforts on preprocessing and formatting.

Four files are available on this site:

train-images-idx3-ubyte.gz:  training set images (9912422 bytes)
train-labels-idx1-ubyte.gz: 
training set labels (28881 bytes)

t10k-images-idx3-ubyte.gz:  
test set images (1648877 bytes)

t10k-labels-idx1-ubyte.gz:  
test set labels (4542 bytes)

FILE FORMATS FOR THE MNIST DATABASE

The data is stored in a very simple file format designed for storing vectors and multidimensional matrices. General info on this format is given at the end of this page, but you don't need to read that to use the data files.

All the integers in the files are stored in the MSB first (high endian) format used by most non-Intel processors. Users of Intel processors and other low-endian machines must flip the bytes of the header.

There are 4 files:

train-images-idx3-ubyte: training set images
train-labels-idx1-ubyte: training set labels

t10k-images-idx3-ubyte:  test set images

t10k-labels-idx1-ubyte:  test set labels

The training set contains 60000 examples, and the test set 10000 examples.

The first 5000 examples of the test set are taken from the original
NIST training set. The last 5000 are taken from the original NIST test
set. The first 5000 are cleaner and easier than the last 5000.

TRAINING SET LABEL FILE (train-labels-idx1-ubyte):

[offset] [type]         
[value]          [description]

0000     32 bit integer  0x00000801(2049)
magic number (MSB first)

0004     32 bit integer  60000           
number of items

0008     unsigned byte   ??              
label

0009     unsigned byte   ??              
label

........

xxxx     unsigned byte   ??              
label

The labels values are 0 to 9.

TRAINING SET IMAGE FILE (train-images-idx3-ubyte):

[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

Pixels are organized row-wise. Pixel values are 0 to 255. 0 means background
(white), 255 means foreground (black).

TEST SET LABEL FILE (t10k-labels-idx1-ubyte):

[offset] [type]         
[value]          [description]

0000     32 bit integer  0x00000801(2049)
magic number (MSB first)

0004     32 bit integer  10000           
number of items

0008     unsigned byte   ??              
label

0009     unsigned byte   ??              
label

........

xxxx     unsigned byte   ??              
label

The labels values are 0 to 9.

TEST SET IMAGE FILE (t10k-images-idx3-ubyte):

[offset] [type]         
[value]          [description]

0000     32 bit integer  0x00000803(2051)
magic number

0004     32 bit integer  10000           
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

Pixels are organized row-wise. Pixel values are 0 to 255. 0 means background
(white), 255 means foreground (black).

---

THE IDX FILE FORMAT

the IDX file format is a simple format for vectors and multidimensional
matrices of various numerical types.

The basic format is

magic number

size in dimension 0

size in dimension 1

size in dimension 2

.....

size in dimension N

data

The magic number is an integer (MSB first). The first 2 bytes are always
0.

The third byte codes the type of the data:

0x08: unsigned byte

0x09: signed byte

0x0B: short (2 bytes)

0x0C: int (4 bytes)

0x0D: float (4 bytes)

0x0E: double (8 bytes)

The 4-th byte codes the number of dimensions of the vector/matrix: 1
for vectors, 2 for matrices....

The sizes in each dimension are 4-byte integers (MSB first, high endian,
like in most non-Intel processors).

The data is stored like in a C array, i.e. the index in the last dimension
changes the fastest.