matlab如何获取png格式的fashion mnist数据集

可以通过以下步骤在Matlab中获取Fashion MNIST数据集：

1. 在Matlab中打开命令窗口，输入以下命令下载Fashion MNIST数据集：

urlwrite('https://github.com/zalandoresearch/fashion-mnist/raw/master/data/fashion/t10k-images-idx3-ubyte.gz','t10k-images-idx3-ubyte.gz');
urlwrite('https://github.com/zalandoresearch/fashion-mnist/raw/master/data/fashion/t10k-labels-idx1-ubyte.gz','t10k-labels-idx1-ubyte.gz');
urlwrite('https://github.com/zalandoresearch/fashion-mnist/raw/master/data/fashion/train-images-idx3-ubyte.gz','train-images-idx3-ubyte.gz');
urlwrite('https://github.com/zalandoresearch/fashion-mnist/raw/master/data/fashion/train-labels-idx1-ubyte.gz','train-labels-idx1-ubyte.gz');

2. 解压缩下载的文件，可以使用以下命令：

gunzip t10k-images-idx3-ubyte.gz
gunzip t10k-labels-idx1-ubyte.gz
gunzip train-images-idx3-ubyte.gz
gunzip train-labels-idx1-ubyte.gz

3. 加载图片和标签数据：

test_images = processImages('t10k-images-idx3-ubyte');
test_labels = processLabels('t10k-labels-idx1-ubyte');
train_images = processImages('train-images-idx3-ubyte');
train_labels = processLabels('train-labels-idx1-ubyte');

其中，`processImages`和`processLabels`是两个自定义函数，用于解析数据集文件并返回图像和标签数据。这两个函数的代码如下：

function images = processImages(filename)
    fid = fopen(filename,'r','b');
    if fid == -1
        error('Error: Cannot open file %s',filename);
    end
    magicNumber = fread(fid,1,'int32',0,'b');
    numImages = fread(fid,1,'int32',0,'b');
    numRows = fread(fid,1,'int32',0,'b');
    numCols = fread(fid,1,'int32',0,'b');
    images = fread(fid,inf,'unsigned char');
    images = reshape(images,numCols,numRows,numImages);
    images = permute(images,[2 1 3]);
    fclose(fid);
end

function labels = processLabels(filename)
    fid = fopen(filename,'r','b');
    if fid == -1
        error('Error: Cannot open file %s',filename);
    end
    magicNumber = fread(fid,1,'int32',0,'b');
    numItems = fread(fid,1,'int32',0,'b');
    labels = fread(fid,inf,'unsigned char');
    fclose(fid);
end

4. 将图像数据转换为PNG格式：

for i = 1:size(test_images,3)
    imwrite(test_images(:,:,i),sprintf('test_%d.png',i));
end
for i = 1:size(train_images,3)
    imwrite(train_images(:,:,i),sprintf('train_%d.png',i));
end

这将把每个图像保存为一个PNG格式的文件。