private Complex[] ft(byte[] img, int width, int height, boolean withoutCentering) {
Complex[] F = new Complex[width * height];
for (int u = 0; u < height; u++) {
for (int v = 0; v < width; v++) {
F[u * width + v] = new Complex();
for (int x = 0; x < height; x++) {
for (int y = 0; y < width; y++) {
double a =
(double) (img[x * width + y] & 0xFF) * (withoutCentering ? 1 : Math.pow(-1, x + y));
double b = -2.0 * Math.PI * (u * x / (double) height + v * y / (double) width);
Complex c = Complex.fromPolar(1, b).mul(a);
F[u * width + v] = F[u * width + v].plus(c);
}
}
}
}
return F;
}
private void ift(Complex[] F, byte[] img, int width, int height) {
for (int x = 0; x < height; x++) {
for (int y = 0; y < width; y++) {
Complex c = new Complex();
for (int u = 0; u < height; u++) {
for (int v = 0; v < width; v++) {
Complex tmp =
Complex.fromPolar(
1, 2.0 * Math.PI * (u * x / (double) height + v * y / (double) width));
c = c.plus(tmp.mul(F[u * width + v]));
}
}
c = c.div(height * width);
c = c.mul(Math.pow(-1, (x + y)));
if (c.getReal() < 0) c.setReal(0.0);
System.out.println(c.getReal());
img[x * width + y] = (byte) (c.getReal());
}
}
}