void fft_shift_x(image_type& I)
{
int half_w = I.width() >> 1;
int half_w_1 = half_w-1;
int w_1 = I.width()-1;
int quater_w = half_w >> 1;
typename image_type::iterator iter1 = I.begin();
typename image_type::iterator end = I.end();
for(;iter1 != end;iter1 += I.width())
{
typename image_type::iterator iter2 = iter1+half_w;
for(int x = 0,rx = half_w_1;x < quater_w;++x,--rx)
{
std::swap(iter1[x],iter1[rx]);
std::swap(iter2[x],iter2[rx]);
}
}
}
void fft_shift_y(image_type& I)
{
int w = I.width();
int half_wh = I.plane_size() >> 1;
int half_wh_1 = half_wh-w;
int quater_wh = half_wh >> 1;
typename image_type::iterator iter1 = I.begin();
typename image_type::iterator end = I.end();
for(;iter1 != end;iter1 += I.plane_size())
{
typename image_type::iterator iter1_x = iter1;
typename image_type::iterator iter1_x_end = iter1+w;
typename image_type::iterator iter2_x = iter1_x+half_wh;
for(;iter1_x != iter1_x_end;++iter1_x,++iter2_x)
for(int y = 0,ry = half_wh_1;y < quater_wh;y+=w,ry-=w)
{
std::swap(iter1_x[y],iter1_x[ry]);
std::swap(iter2_x[y],iter2_x[ry]);
}
}
}