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
task1.rar （12个子文件） 
task1 
rose.tif 1MB re256×256.tif 737KB re128×128.tif 541KB re512×512.tif 342KB re64×64.tif 411KB 32×32.tif 1KB 64×64.tif 4KB 128×128.tif 16KB re32×32.tif 342KB 256×256.tif 64KB task1.m 4KB 512×512.tif 255KB资源评论
