manual bilinear and nearest neighbor interpolation

Hi , i am trying to perform nearest neighbor and bilinear interpolation on a 512*512 image to convert into 1024*1024 as well as 768*768 . i got some code but not able to proceed further with errors such as "undefined function for input argument double" please help me to convert to 1024*1024 as well as 768*768 without using imresize

here is the following code and attached is the image

inputI= imread('lenatest3.jpg');

[r c] = size(inputI);

scale=2;

for i=1: scale *r

 for j=1: scale *c

% map from output image location to input image location by nearest neighbor

 ii = round( (i-1)*(r-1)/( scale *r-1)+1 ); 

 jj = round( (j-1)*(c-1)/( scale *c-1)+1 ); 

 % assign value 

 nni(i,j) = inputI(ii,jj); 

 end

end

% bilinear

scale=2;

blin=uint8(zeros(r*scale,c*scale));

for i=1:1:size(blin,1)-scale

for j=1:1:size(blin,2)-scale

A=im(ceil(i/scale),ceil(j/scale));

B=im(ceil(i/scale)+1,ceil(j/scale));

C=im(ceil(i/scale),ceil(j/scale)+1);

D=im(ceil(i/scale)+1,ceil(j/scale)+1);

ii=mod(i-1,scale)/scale;

jj=mod(j-1,scale)/scale;

blin(i,j)=A+ii*(B-A)+jj*(C-A+ii*(D+A-C-B));

end

end

Answer 1

[Image Analyst]

Don't do any of that. Simply call imresize().

[tilak tenneti]

thank you sir but as a task of my work i am required to do the manual task of achieving bilinear and nearest neighbor without using imresize().

any help would be appreciated

thanks

[Image Analyst]

Why? Is this homework? You didn't tag it as homework. How about interp2()? Or is that not allowed either? Maybe I'll have time to look at it later....