C语言实现快速傅里叶变换的算法
快速傅立叶/余弦/正弦变换
尺寸：一个
数据长度：2的幂
抽取：频率
基数：4，2
函数：
cdft：复数离散傅立叶变换
rdft：实离散傅里叶变换
ddct：离散余弦变换
ddst：离散正弦变换
dfct：RDFT（实对称DFT）的余弦变换
dfst：RDFT（实反对称DFT）的正弦变换
函数原型：
void cdft(int, int, double *, int *, double *); // 复数离散傅立叶变换
void rdft(int, int, double *, int *, double *); // 实离散傅里叶变换
void ddct(int, int, double *, int *, double *); // 离散余弦变换
void ddst(int, int, double *, int *, double *); // 离散正弦变换
void dfct(int, double *, double *, int *, double *); // 实对称DFT
void dfst(int, double *, double *, int *, double *); // 实反对称DFT
void cdft(int n, int isgn, double *a, int *ip, double *w)
{
if (n > (ip[0] << 2)) {
makewt(n >> 2, ip, w);
}
if (n > 4) {
if (isgn >= 0) {
bitrv2(n, ip + 2, a);
cftfsub(n, a, w);
} else {
bitrv2conj(n, ip + 2, a);
cftbsub(n, a, w);
}
} else if (n == 4) {
cftfsub(n, a, w);
}
}
void rdft(int n, int isgn, double *a, int *ip, double *w)
{
int nw, nc;
double xi;
nw = ip[0];
if (n > (nw << 2)) {
nw = n >> 2;
makewt(nw, ip, w);
}
nc = ip[1];
if (n > (nc << 2)) {
nc = n >> 2;
makect(nc, ip, w + nw);
}
if (isgn >= 0) {
if (n > 4) {
bitrv2(n, ip + 2, a);
cftfsub(n, a, w);
rftfsub(n, a, nc, w + nw);
} else if (n == 4) {
cftfsub(n, a, w);
}
xi = a[0] - a[1];
a[0] += a[1];
a[1] = xi;
} else {
a[1] = 0.5 * (a[0] - a[1]);
a[0] -= a[1];
if (n > 4) {
rftbsub(n, a, nc, w + nw);
bitrv2(n, ip + 2, a);
cftbsub(n, a, w);
} else if (n == 4) {
cftfsub(n, a, w);
}
}
}
void ddct(int n, int isgn, double *a, int *ip, double *w)
{
int j, nw, nc;
double xr;
nw = ip[0];
if (n > (nw << 2)) {
nw = n >> 2;
makewt(nw, ip, w);
}
nc = ip[1];
if (n > nc) {
nc = n;
makect(nc, ip, w + nw);
}
if (isgn < 0) {
xr = a[n - 1];
for (j = n - 2; j >= 2; j -= 2) {
a[j + 1] = a[j] - a[j - 1];
a[j] += a[j - 1];
}
a[1] = a[0] - xr;
a[0] += xr;
if (n > 4) {
rftbsub(n, a, nc, w + nw);
bitrv2(n, ip + 2, a);
cftbsub(n, a, w);
} else if (n == 4) {
cftfsub(n, a, w);
}
}
dctsub(n, a, nc, w + nw);
if (isgn >= 0) {
if (n > 4) {
bitrv2(n, ip + 2, a);
cftfsub(n, a, w);
rftfsub(n, a, nc, w + nw);
} else if (n == 4) {
cftfsub(n, a, w);
}
xr = a[0] - a[1];
a[0] += a[1];
for (j = 2; j < n; j += 2) {
a[j - 1] = a[j] - a[j + 1];
a[j] += a[j + 1];
}
a[n - 1] = xr;
}
}
void ddst(int n, int isgn, double *a, int *ip, double *w)
{
int j, nw, nc;
double xr;
nw = ip[0];
if (n > (nw << 2)) {
nw = n >> 2;
makewt(nw, ip, w);
}
nc = ip[1];
if (n > nc) {
nc = n;
makect(nc, ip, w + nw);
}
if (isgn < 0) {
xr = a[n - 1];
for (j = n - 2; j >= 2; j -= 2) {
a[j + 1] = -a[j] - a[j - 1];
a[j] -= a[j - 1];
}
a[1] = a[0] + xr;
a[0] -= xr;
if (n > 4) {
rftbsub(n, a, nc, w + nw);
bitrv2(n, ip + 2, a);
cftbsub(n, a, w);
} else if (n == 4) {
cftfsub(n, a, w);
}
}
dstsub(n, a, nc, w + nw);
if (isgn >= 0) {
if (n > 4) {
bitrv2(n, ip + 2, a);
cftfsub(n, a, w);
rftfsub(n, a, nc, w + nw);
} else if (n == 4) {
cftfsub(n, a, w);
}
xr = a[0] - a[1];
a[0] += a[1];
for (j = 2; j < n; j += 2) {
a[j - 1] = -a[j] - a[j + 1];
a[j] -= a[j + 1];
}
a[n - 1] = -xr;
}
}
void dfct(int n, double *a, double *t, int *ip, double *w)
{
int j, k, l, m, mh, nw, nc;
double xr, xi, yr, yi;
nw = ip[0];
if (n > (nw << 3)) {
nw = n >> 3;
makewt(nw, ip, w);
}
nc = ip[1];
if (n > (nc << 1)) {
nc = n >> 1;
makect(nc, ip, w + nw);
}
m = n >> 1;
yi = a[m];
xi = a[0] + a[n];
a[0] -= a[n];
t[0] = xi - yi;
t[m] = xi + yi;
if (n > 2) {
mh = m >> 1;
for (j = 1; j < mh; j++) {
k = m - j;
xr = a[j] - a[n - j];
xi = a[j] + a[n - j];
yr = a[k] - a[n - k];
yi = a[k] + a[n - k];
a[j] = xr;
a[k] = yr;
t[j] = xi - yi;
t[k] = xi + yi;
}
t[mh] = a[mh] + a[n - mh];
a[mh] -= a[n - mh];
dctsub(m, a, nc, w + nw);
if (m > 4) {
bitrv2(m, ip + 2, a);
cftfsub(m, a, w);
rftfsub(m, a, nc, w + nw);
} else if (m == 4) {
cftfsub(m, a, w);
}
a[n - 1] = a[0] - a[1];
a[1] = a[0] + a[1];
for (j = m - 2; j >= 2; j -= 2) {
a[2 * j + 1] = a[j] + a[j + 1];
a[2 * j - 1] = a[j] - a[j + 1];
}
l = 2;
m = mh;
while (m >= 2) {
dctsub(m, t, nc, w + nw);
if (m > 4) {
bitrv2(m, ip + 2, t);
cftfsub(m, t, w);
rftfsub(m, t, nc, w + nw);
} else if (m == 4) {
cftfsub(m, t, w);
}
a[n - l] = t[0] - t[1];
a[l] = t[0] + t[1];
k = 0;
for (j = 2; j < m; j += 2) {
k += l << 2;
a[k - l] = t[j] - t[j + 1];
a[k + l] = t[j] + t[j + 1];
}
l <<= 1;
mh = m >> 1;
for (j = 0; j < mh; j++) {
k = m - j;
t[j] = t[m + k] - t[m + j];
t[k] = t[m + k] + t[m + j];
}
t[mh] = t[m + mh];
m = mh;
}
a[l] = t[0];
a[n] = t[2] - t[1];
a[0] = t[2] + t[1];
} else {
a[1] = a[0];
a[2] = t[0];
a[0] = t[1];
}
}
void dfst(int n, double *a, double *t, int *ip, double *w)
{
int j, k, l, m, mh, nw, nc;
double xr, xi, yr, yi;
nw = ip[0];
if (n > (nw << 3)) {
nw = n >> 3;
makewt(nw, ip, w);
}
nc = ip[1];
if (n > (nc << 1)) {
nc = n >> 1;
makect(nc, ip, w + nw);
}
if (n > 2) {
m = n >> 1;
mh = m >> 1;
for (j = 1; j < mh; j++) {
k = m - j;
xr = a[j] + a[n - j];
xi = a[j] - a[n - j];
yr = a[k] + a[n - k];
yi = a[k] - a[n - k];
a[j] = xr;
a[k] = yr;
t[j] = xi + yi;
t[k] = xi - yi;
}
t[0] = a[mh] - a[n - mh];
a[mh] += a[n - mh];
a[0] = a[m];
dstsub(m, a, nc, w + nw);
if (m > 4) {
bitrv2(m, ip + 2, a);
cftfsub(m, a, w);
rftfsub(m, a, nc, w + nw);
} else if (m == 4) {
cftfsub(m, a, w);
}
a[n - 1] = a[1] - a[0];
a[1] = a[0] + a[1];
for (j = m - 2; j >= 2; j -= 2) {
a[2 * j + 1] = a[j] - a[j + 1];
a[2 * j - 1] = -a[j] - a[j + 1];
}
l = 2;
m = mh;
while (m >= 2) {
dstsub(m, t, nc, w + nw);
if (m > 4) {
bitrv2(m, ip + 2, t);
cftfsub(m, t, w);
rftfsub(m, t, nc, w + nw);
} else if (m == 4) {
cftfsub(m, t, w);
}
a[n - l] = t[1] - t[0];
a[l] = t[0] + t[1];
k = 0;
for (j = 2; j < m; j += 2) {
k += l << 2;
a[k - l] = -t[j] - t[j + 1];
a[k + l] = t[j] - t[j + 1];
}
l <<= 1;
mh = m >> 1;
for (j = 1; j < mh; j++) {
k = m - j;
t[j] = t[m + k] + t[m + j];
t[k] = t[m + k] - t[m + j];
}
t[0] = t[m + mh];
m = mh;
}
a[l] = t[0];
}
a[0] = 0;
}