matlab实现图像下采样和双线性插值

clear %读取图像 image=imread('rose.tif'); %已知原图为1024*1024，为了直观下文直接使用1024进行计算，而不是带入width, heigh % [width, heigh] = size(image); % 显示原图 figure imshow(image); title('1024×1024') ; %开始下采样 for i = 1 : 5 %下采样率rate为2，4，8，16，32 rate=2.^i; Timage=zeros(1024/rate,1024/rate); for j = 1:1024/rate for k = 1:1024/rate % pixel为原图对应矩阵内灰度的平均值 % pixel=image(j*rate,k*rate); Timage(j,k)= pixel; end end %显示下采样图像并输出图像 figure imshow(uint8(Timage)); if i == 1 title('512×512'); imwrite(uint8(Timage),'512×512.tif'); elseif i == 2 title('256×256'); imwrite(uint8(Timage),'256×256.tif'); elseif i == 3 title('128×128'); imwrite(uint8(Timage),'128×128.tif'); elseif i == 4 title('64×64'); imwrite(uint8(Timage),'64×64.tif'); elseif i == 5 title('32×32'); imwrite(uint8(Timage),'32×32.tif'); end end P=zeros(1,5); % 双线性插值进行放大 for i = 1:5 rate=2^i; reimage = zeros(1024,1024); %读取图像 if i == 1 Timage= imread('512×512.tif'); elseif i == 2 Timage= imread('256×256.tif'); elseif i == 3 Timage= imread('128×128.tif'); elseif i == 4 Timage= imread('64×64.tif'); elseif i == 5 Timage= imread('32×32.tif'); end for j = 1:1024 for k = 1:1024 %如果像素点在“回形框”内，直接取所在窗口的中心点灰度值为自己的像素值，不参与双线性插值 if j< rate/2 +0.5 && k<1024.5-rate/2 reimage(j,k)= uint8(Timage(1,fix(k/rate+1))); elseif j> rate/2 +0.5 && k<rate/2 +0.5 reimage(j,k)=uint8(Timage(fix(j/rate+0.5),1)); elseif j> 1024.5-rate/2 && k> rate/2 +0.5 reimage(j,k)=uint8(Timage(1024/rate,fix(k/rate+0.5))); elseif j<1024.5-rate/2 && k> 1024.5-rate/2 reimage(j,k)=uint8(Timage(fix(j/rate+1),1024/rate)); elseif j> rate/2 +0.5 && j<1024.5-rate/2 && k> rate/2 +0.5 && k<1024.5-rate/2 %其他位置参与双线性插值 %m是作为插值的参考点的左上角点对应在下采样图中的行坐标 m = fix((j-0.5)/rate + 0.5 ); %mm1是作为插值的参考点的左上角点对应在复原图中的行坐标 mm1=(m-0.5)*rate +0.5; mm2=mm1+rate; %n是作为插值的参考点的左上角点对应在下采样图中的列坐标 n = fix((k-0.5)/rate + 0.5 ); %nn1是作为插值的参考点的左上角点对应在复原图中的列坐标 nn1=(n-0.5)*rate +0.5; nn2=nn1+rate; Timage=double(Timage); reimage(j,k)= (mm2-j)*(nn2-k)*Timage(m,n)+(k-nn1)*(mm2-j)*Timage(m,n+1)+(j-mm1)*(k-nn1)*Timage(m+1,n+1)+(nn2-k)*(j-mm1)*Timage(m+1,n); reimage(j,k)=fix(reimage(j,k)/rate/rate); end end end reimage=uint8(reimage); figure imshow( reimage ); if i == 5 title('re512×512'); imwrite(reimage,'re512×512.tif'); %%%%计算PSNR k = 8; %k为图像是表示地个像素点所用的二进制位数，即位深。 fmax = 2.^k - 1; a = fmax.^2; MSE =(double(im2uint8(reimage)) -double( im2uint8(image))).^2; b = mean(mean(MSE)); PSNR = 10*log10(a/b); elseif i == 2 title('re256×256'); imwrite(reimage,'re256×256.tif'); elseif i == 3 title('re128×128'); imwrite(reimage,'re128×128.tif'); elseif i == 4 title('re64×64'); imwrite(reimage,'re64×64.tif'); elseif i == 5 title('re32×32'); imwrite(reimage,'re32×32.tif'); end end