双线性插值法缩放图像函数MATLAB程序(精)

% Define a function for shrinking and zooming images by bilinear interpolation

% I is the original image and N is the factor for shrinking firstly and zooming later function interpolation_shrink_zoom_image(I, N

% First to shrink the original image

% To measure the size of original image I

[P,Q]=size(I;

% Rebuild the original image I to I_TEMP for bilinear interpolation

I_TEMP=zeros(P+2,Q+2; I_TEMP(2:P+1,2:Q+1=I;

I_TEMP(1,2:Q+1=I(1,:; I_TEMP(P+2,2:Q+1=I(P,:;

I_TEMP(2:P+1,1=I(:,1; I_TEMP(2:P+1,Q+2=I(:,Q;

I_TEMP(1,1=I(1,1; I_TEMP(1,P+2=I(1,P;

I_TEMP(P+2,1=I(P,1; I_TEMP(P+2,Q+2=I(P,Q;

I_TEMP=double(I_TEMP;

% To fix the size of shrunken image

% R is the number of rows and C is the number of columns

R=floor(P/N; C=floor(Q/N;

% Define the shrunken image

I_S=zeros(R,C;

% For bilinear interpolation f(x,y in 4 points f(x1,y1,f(x2,y1,f(x1,y2,f(x2,y2 % f(x,y = f(x1,y1*(x2-x*(y2-y/((x2-x1*(y2-y1

% + f(x2,y1*(x-x1*(y2-y/((x2-x1*(y2-y1

% + f(x1,y2*(x2-x*(y-y1/((x2-x1*(y2-y1

% + f(x2,y2*(x-x1*(y-y1/((x2-x1*(y2-y1

% For pixel matrix, x2=x1+1, y2=y1+1, x=x1+a, y=y1+b

% Let x1=u, y1=v, then x2=u+1, y2=v+1, x=u+a, y=v+b

% Then f(u+a, v+b = f(u,v*(1-a*(1-b + f(u+1,v*a*(1-b

% + f(u,v+1*(1-a*b + f(u+1,v+1*a*b

% Method: from original image I get suitable gray value by surrounding 4 pixels,

% then fill the gray value into certain location in shrunken image I_S.

for i=1:R;

for j=1:C;

% Step1: get x,y,u,v,a,b. The size of I to size of I_S ratio = N,

% (x,y is pixel "in" I and (i,j is pixel in I_S, then x/i=y/j=N.

x=i*N; y=j*N; u=floor(x; v=floor(y; a=x-u; b=y-v;

% Step2: considering the situation on bound of I, using I_TEMP to get suitable value of f(x,y by bilinear interpolation

I_S(i,j = I_TEMP(u+1,v+1*(1-a*(1-b + I_TEMP(u+2,v+1*a*(1-b +

I_TEMP(u+1,v+2*(1-a*b + I_TEMP(u+2,v+2*a*b;

end ;

end ;

% Display the original image I and the shrunken image I_S

I_S=uint8(I_S;

figure; imshow(I,[]; title(['Original image: ',num2str(P,'*',num2str(Q]; figure; imshow(I_S,[]; title(['Interpolation shrinking image:

' ,num2str(R,'*',num2str(C];

% Second to zoom the shrunken image

% R*C is the size of shrunken image as shown before

% Rebuild the shrunken image I_S to I_TEMP for bilinear interpolation I_TEMP=zeros(R+2,C+2; I_TEMP(2:R+1,2:C+1=I_S;

I_TEMP(1,2:C+1=I_S(1,:; I_TEMP(R+2,2:C+1=I_S(R,:;

I_TEMP(2:R+1,1=I_S(:,1; I_TEMP(2:R+1,C+2=I_S(:,C;

I_TEMP(1,1=I_S(1,1; I_TEMP(1,R+2=I_S(1,R;

I_TEMP(R+2,1=I_S(R,1; I_TEMP(R+2,R+2=I_S(R,C;

I_TEMP=double(I_TEMP;

% Define the zoomed image

I_Z=zeros(R*N,C*N;