Help with interpolation code

[mantale1]

Hi all,

   I have some experience with MATLAB/Octave but I keep getting some
unexpected errors when I try to write a simple program that uses either
bilinear or nearest-neighbor interpolation. Here is the code:

function r = pv(im, x, y, method)
%get pixel value using interpolation
method = char(method);
[rows, cols] = size(im);
im = double(im);
H = rows;
W = cols;


if (x>=1) && (x<=W) && (y>=1) && (y<=H),
        %point is in picture
        if method == 'bilinear',
                xd = floor(x);
                xup = ceil(x);
                yd = floor(y);
                yup = ceil(y);
                %pretend on unit square, construct mat with corner vals
                Q = [im(yd,xd) im(yd,xup);...
                im(yup,xd) im(yup,xup)];
                r = [1 - mod(x,xd) mod(x,xd)] * Q * [1 - mod(y,yd); mod(y,yd)];
        else %method == 'nearest',
                r = im(round(y), round(x));
        end
else %(x,y) not in image
        r = 0;
end


When method is set to 'bilinear' the interpolation works fine, but when I
try to use 'nearest' I get an error saying:

mx_el_eq:nonconformant arguments (op1 is 1 x 7, op2 is 1 x8)

I honestly have no idea why I am getting this. Any ideas?



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