Re: Nearest neighbor interpolation.

[Ismael Núñez-Riboni]

On 04/20/2012 09:40 AM, rikydzee wrote:
> Hy there, i need some help. I have a matrix obtained from a picture, let's
> say that my matrix is [1 2 3 ; 4 5 6 ; 7 8 9] and i need to transform this
> matrix into [ 1 0 2 0 3; 0 0 0 0 0 ; 4 0 5 0 6 ; 0 0 0 0 0; 7 0 8 0 9 ]. I
> managed to do that making another matrix filled with zeros and put pixel by
> pixel from first matrix in the second one.

You mean here with a double for-loop? Yes, this might be not very 
efficient in Octave, but I see no other way to do it, particularly not 
with nearest neighbor interpolation... With nearest neighbor 
interpolation you will never get zeros in your interpolated matrix, 
since the interpolation algorithm always looks for a value (i.e. the 
nearest one).

I can suggest to reduce the two for-loops to one to make it faster:

a = [1 2 3 ; 4 5 6 ; 7 8 9];

b = zeros(2.*size(a,1), 2.*size(a,2));

for i =  1:size(a,1)
   b(2.*i-1,1:2:end) = a(i,:);
end

Have luck, Ismael.