You have first to make the source of that package, written in pure
ISO standard C, available. You can publish it on some appropriate
URL if it is too large to post here (i.e. over about 200 lines or
so). I have no idea if such action is permitted to you. Then you
can see if anyone is willing to attack it. Include the available
documentation.
Don't be silly.
Some people here won't know what a Fourier transform is, but it is
sufficiently fundamental to assume that most people will.
We know that Stephen is using a Fourier transform on images. So he needs to
pass a 2-dimensional real array to the transform, and he will get a
2-dimensional complex result out. So all we need is the prototype of the
fftw fucntions, and we can tell him how to call it.
What he need to do is
1) Call a bitmap loading fucntion, such as the one I provided.
eg
unsigned char *rgb;
int width, height;
float *red;
int i, ii;
rgb = loadbmp("directory\\myfile.bmp", &width, &height);
if(!rgb)
{
/* didn't load */
}
2)
/* Now make the rgb pixel values into real numbers, range 0-1 */
red = malloc(width * height * sizeof(float));
for(i=0;i<height;i++)
for(ii=0;ii<width;ii++)
red[i*width+ii] = rgb[i * width * 3 + ii * 3]/ 255.0f;
3)
/* now we need the fftw prototype to know how to get out data into the right
format */
This bit we cannot yet do without the function prototype. Often you need to
pad to powers of 2, and probably the fucntions inist on input as well as
output being complex - which means setting the imaginary part to 0.