clear all;
I = imread('lena.bmp');
figure; imshow(I);title('原图像');
[m,n]=size(I);
%%% 缩小 临近法
M = 0.5; %放大倍数
%新的图像大小
m1=m*M;n1=n*M;
%****************************************************
for i=1:m1
for j=1:n1;
J(i,j)=I(round(i/M),round(j/M));
end
end
%*****************************************************
figure; imshow(J);title('缩小图像');
%%% 放大 双线性插值法
I2 = double(I);
N = 1.5; %放大倍数
%新的图像大小
m2=m*N;n2=n*N;
J2=zeros(m2,n2);
for i=1:m2
for j=1:n2
x=i/N;
y=j/N;
u=floor(x);
v=floor(y);
a=x-u;
b=y-v;
if u+2<=m & v+2<=n
J2(i,j)=I2(u+1,v+1)*(1-a)*(1-b)+I2(u+2,v+1)*a*(1-b)+I2(u+1,v+2)*(1-a)*b+I2(u+2,v+2)*a*b;
end
end
end
J2 = uint8(J2);
figure;imshow(J2);title('放大图像');
%%%%% 旋转
R = 45*pi/180; %旋转角度
I = double(I);
%新图像大小
m2 = ceil(m*cos(R)+n*sin(R));
n2 = ceil(m*sin(R)+n*cos(R));
u0= m*sin(R);%平移量
%变换矩阵
T=[cos(R),sin(R);-sin(R),cos(R)];
L = zeros(m2,n2);
for u=1:n2
for v=1:m2
%新图像坐标变换到原图像坐标x和y中
temp = T*([u;v]-[u0;0]);
x= temp(1);
y= temp(2);
if x>=1 & x<=m & y>=1 & y<=n %若变换出的x和y在原图像范围内
x_low=floor(x);
x_up=ceil(x);
y_low=floor(y);
y_up=ceil(y);
%双线性插值,p1到p4是(x,y)周围的四个点
p1=I(x_low,y_low);
p2=I(x_up,y_low);
p3=I(x_low,y_low);
p4=I(x_up,y_up);
s=x-x_low;
t=y-y_low;
L(u,v)=(1-s)*(1-t)*p1+(1-s)*t*p3+(1-t)*s*p2+s*t*p4;
end
end
end
L=uint8(L);
figure;imshow(L);
![](https://video.ask-data.xyz/img.php?b=https://iknow-pic.cdn.bcebos.com/42a98226cffc1e171970d25a4990f603728de98a?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)