How to enlarge an image using spline interpolation

I want to double the size of the input image using "spline". Please tell me how

Answer 1

[KSSV]

I = imread("image.jpeg") ;  % assuming image to m*n
[m,n,p] = size(I) ; 
x = 1:n ;
y = 1:m ; 
% Inteprolate to double
xi = 1:2*n ;
yi = 1:2*m ;
I = double(I) ; 
Inew = zeros(2*m,2*n) ; 
% Row wise inteprolation 
for i = 1:m
  Inew(i,:) = spline(x,I(i,:),xi) ; 
end
% Column wise interpolation 
for j = 1:n
  Inew(:,j) = spline(y,I(:,j),yi) ; 
end

Change the class if Inew to the original I. Also read about imresize.

[T.K]

I'm sorry to reply your comment.

Thank you for helping me.

But I didn't work.

inputimageoutputimage

I = imread("lenna.jpg") ;  % assuming image to m*n
I=rgb2gray(I);
[m,n,] = size(I) ; 
x = 1:n ;
y = 1:m ; 
% Inteprolate to double
xi = 1:2*n ;
yi = 1:2*m ;
I = double(I) ; 
Inew = zeros(2*m,2*n) ; 
% Row wise inteprolation 
for i = 1:m
  Inew(i,:) = spline(x,I(i,:),xi) ; 
end
% Column wise interpolation 
for j = 1:n
  Inew(:,j) = spline(y,I(:,j),yi) ; 
end

figure
    imshow(Inew)

[KSSV]

Check the below code:

I = imread("image.jpeg") ;  % assuming image to m*n
I=rgb2gray(I);
[m,n] = size(I) ; 
x = 1:n ;
y = 1:m ; 
% Inteprolate to double
xi = linspace(1,n,2*n) ;
yi = linspace(1,m,2*m) ;
I = double(I) ; 
I1 = zeros(m,2*n) ; 
% Row wise inteprolation 
for i = 1:m
  I1(i,:) = spline(x,I(i,:),xi) ; 
end
Inew = zeros(2*m,2*n) ; 
% Column wise interpolation 
for j = 1:2*n
  Inew(:,j) = spline(y,I1(:,j),yi) ; 
end
Inew = uint8(Inew) ; 
figure
imshow(Inew)

[T.K]

Thank you for your replying.

I succeeded thanks to you.

What was the cause of the failure?

[KSSV]

You can see both the codes given..there are few mistakes int he first code which have been rectiffied. Especially generating the new grid fot enlarging the image.

Thanks is accepting/ voting the answer.

[T.K]

Thank you for your replying!

I understood!

Answer 2

[Bruno Luong]

A=peaks(10);

B=interp2(A,1,'spline');

subplot(1,2,1)
imagesc(A)
subplot(1,2,2)
imagesc(B)