how program discrete fourier transform

hi ! I want to program a discrete Fourier transform to detect the outline of an image

Z(K)= p(k) exp(j*2*pi*l*k)/n

l=0,1.....n-1

Z=>fourier transform

p(k)=>Representation of the border of the object in an unidimensionnel space p(l)=x(l)+jy(l)

(l=0,1....n-1)

j=sqrt-1

help please

[Iain]

Look up fft in the help...