In [1]:
using FixedPointNumbers;
The following is taken from THE MNIST DATABASE of handwritten digits:
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:
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).
In [2]:
const MNIST_LABELS_MAGIC = 0x00000801;
const MNIST_IMAGES_MAGIC = 0x00000803;
In [3]:
function MNIST_read_labels(filename :: AbstractString)
open(filename) do io
magic = ntoh(read(io, UInt32))
if magic != MNIST_LABELS_MAGIC
error("File \"$filename\" contains the wrong magic number for an MNIST labels file, $magic")
end
n = ntoh(read(io, UInt32))
return read(io, Int8, n)
end
end;
In [4]:
function MNIST_read_images(filename :: AbstractString)
open(filename) do io
magic = ntoh(read(io, UInt32))
if magic != MNIST_IMAGES_MAGIC
error("File \"$filename\" contains the wrong magic number for an MNIST images file, $magic")
end
n = ntoh(read(io, UInt32))
rows = Int(ntoh(read(io, UInt32)))
cols = Int(ntoh(read(io, UInt32)))
images = Array{UFixed8}(n, 1 + rows * cols)
for i in 1:n
images[i, 1] = 1
images[i, 2:end] = UFixed8(1) - vec(read(io, UFixed8, (cols, rows)))
end
return (cols, rows, images)
end
end;