有没有人知道怎么用MATLAB压缩图片，还有用霍夫曼编码压缩呀

% 读取图像
img = imread('sample.jpg');

% 将图像转换为灰度图
grayImg = rgb2gray(img);

% 对图像进行离散余弦变换
dctImg = dct2(grayImg);

% 对离散余弦变换后的图像进行霍夫曼编码压缩
huff = huffmandict(double(dctImg(:)), 256);
huffCode = huffmanenco(double(dctImg(:)), huff);

% 解压缩并还原图像
dctImgDecoded = huffmandeco(huffCode, huff);
grayImgDecoded = idct2(reshape(dctImgDecoded, size(grayImg)));
imgDecoded = repmat(grayImgDecoded, [1, 1, 3]);

% 计算压缩前后图像的psnr
psnrVal = psnr(img, imgDecoded);
disp(['The PSNR of the compressed image is: ', num2str(psnrVal)]);

% 将压缩后的图像保存到文件中
imwrite(imgDecoded, 'compressed.jpg');