This function that I wrote is supposed to take the DCT of the input image. The run time is too much which I expect to be because of number of irritations. The picture that im using has 700*500 pixels. As u can see theres 4 nested for loops which makes the number of irritations to be 700*500*700*500 (almost 10^11). its that realy too many irritation for a computer or is there something wrong with the code? if yes what could it be?
function out_image = dct2(in_image)
s = size(in_image);
in_image = double(in_image);
out_image = zeros(s);
for i = 1:s(1)
for j = 1:s(2)
x = 0;
ci = 1;
cj = 1;
if i == 1
ci = sqrt(2)/2;
end
if j == 1
cj = sqrt(2)/2;
end
for m = 1:s(1)
for n = 1:s(2)
a = cos((((2*(m-1))+1)*(i-1)*pi)/(2*s(1)));
b = cos((((2*(n-1))+1)*(j-1)*pi)/(2*s(2)));
x = x + (a * b * in_image(m,n));
end
end
out_image(i,j) = (2/sqrt(s(1)*s(2)))* ci * cj * x;
end
end
end
