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法律研究C++ 对给定的复杂 2D 数组进行就地 2D FFT
快速傅里叶变换 (FFT) 是一个计算离散傅里叶变换 (DFT) 及其逆变换的算法。基本上，傅里叶分析将时间（或空间）转换为频率，反之亦然。FFT 通过将 DFT 矩阵分解为稀疏（大多为零）因子的乘积来快速计算变换。
算法
Begin Declare the size of the array Take the elements of the array Declare three arrays Initialize height =size of array and width=size of array Create two outer loops to iterate on output data Create two outer loops to iterate on input data Compute real, img and amp. End
示例代码
#include <iostream>
#include <math.h>
using namespace std;
#define PI 3.14159265
int n;
int main(int argc, char **argv) {
cout << "Enter the size: ";
cin >> n;
double Data[n][n];
cout << "Enter the 2D elements ";
for (int i = 0; i < n; i++)
for (int j = 0; j < n; j++)
cin >> Data[i][j];
double realOut[n][n];
double imgOut[n][n];
double ampOut[n][n];
int height = n;
int width = n;
for (int yWave = 0; yWave < height; yWave++) {
for (int xWave = 0; xWave < width; xWave++) {
for (int ySpace = 0; ySpace < height; ySpace++) {
for (int xSpace = 0; xSpace < width; xSpace++) {
realOut[yWave][xWave] += (Data[ySpace][xSpace] * cos(2 *
PI * ((1.0 * xWave * xSpace / width) + (1.0 * yWave * ySpace /
height)))) / sqrt(width * height);
imgOut[yWave][xWave] -= (Data[ySpace][xSpace] * sin(2 * PI
* ((1.0 * xWave * xSpace / width) + (1.0 * yWave * ySpace / height)))) /
sqrt( width * height);
ampOut[yWave][xWave] = sqrt(
realOut[yWave][xWave] * realOut[yWave][xWave] +
imgOut[yWave][xWave] * imgOut[yWave][xWave]);
}
cout << realOut[yWave][xWave] << " + " <<
imgOut[yWave][xWave] << " i (" << ampOut[yWave][xWave] << ")\n";
}
}
}
}输出
Enter the size: 2 Enter the 2D elements 4 5 6 7 4.5 + 6.60611e-310 i (4.5) 11 + 6.60611e-310 i (11) -0.5 + -8.97448e-09 i (0.5) -1 + -2.15388e-08 i (1) 4.5 + 6.60611e-310 i (4.5) -2 + -2.33337e-08 i (2) -0.5 + -8.97448e-09 i (0.5) 0 + 5.38469e-09 i (5.38469e-09)
更新于：30-Jul-2019
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