图像处理基础（七）图像的PCA（主成分分析）降维

clear;
clc;
img = imread('test.jpg');
img_gray = rgb2gray(img);

img_gray = imresize(img_gray,0.5);
[m,n] = size(img_gray);
[u,s,v] = svd(double(img_gray));

r = 2;    % 压缩率
K =round(2 * m * n / ( r * (m + n + 1)));

if K > min(m,n)
    K = min(m,n);
end

img_c = zeros(size(img_gray));

for i = 1:K
    img_c = img_c + s(i,i) * u(:,i) * v(:,i)';
end
%subplot(2,2,1); imshow(img,[]); title('origin');
%subplot(2,2,2); imshow(img_gray,[]); title('gray');
subplot(2,2,3); imshow(img_c,[]); title(['zip r = ',num2str(r), ' zip Image']);
imwrite(img_c,'zip.bmp')