%MNIST源文件下載地址http://yann.lecun.com/exdb/mnist/index.html
%功能：將下載得到的二進制文件轉換為10進制數據，提取像素數據和標簽數據
%適用：僅適用于MNIST數據集，修改后可適用于其他
%Create?by?VivienFu?e-mail:vivienfu@163.com

function?output=decodefile（filenametype）
%數據介紹如下，參考網址http://yann.lecun.com/exdb/mnist/index.html

%?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

%?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
fio=fopen（filename‘r‘）;%原始文件中數據是以2進制存儲的。
a?=?fread（fio‘uint8‘）;%以8進制方式讀取源文件。雖然前幾項是32bit的，但是圖像像素數據是8bit的，所以此處用8bit處理。

if?strcmp（type‘image‘）
%?????magic_num=a（1）*256^3+a（2）*256^2+a（3）*256+a（4）;
%?????image_num=a（5）*256^3+a（6）*256^2+a（7）*256+a（8）;
%?????image_rows=a（9）*256^3+a（10）*256^2+a（11）*256+a（12）;%默認訓練和測試圖像都已經reshape到一個size
%?????image_cols=a（13）*256^3+a（14）*256^2+a（15）*256+a（16）;

????output=a（17:end）;%提取像素數據
else?if?strcmp（type‘label‘）
%?????????magic_num=a（1）*256^3+a（2）*256^2+a（3）*256+a（4）;
%?????????image_num=a（5）*256^3+a（6）*256^2+a（7）*256+a（8）;
????????output=a（9:end）;??????
????end
end

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----
?????目錄???????????0??2019-12-29?13:43??MNIST?to?uint8?by?matlab\
?????文件????????3011??2017-01-01?22:41??MNIST?to?uint8?by?matlab\decodefile.m
?????文件????????1275??2017-01-01?22:41??MNIST?to?uint8?by?matlab\mnist_uint8.m