写一个二维离散傅里叶变换的C语言代码

以下是一个简单的二维离散傅里叶变换的C语言实现：

#include <stdio.h>
#include <math.h>

#define N 8 //矩阵大小

void DFT2D(double input[N][N], double output[N][N]) {
    int u, v, x, y;
    double sum_real, sum_imag;
    double W_real, W_imag;

    for (u = 0; u < N; u++) {
        for (v = 0; v < N; v++) {
            sum_real = 0.0;
            sum_imag = 0.0;

            for (x = 0; x < N; x++) {
                for (y = 0; y < N; y++) {
                    W_real = cos(2 * M_PI * ((double)(u * x) / N + (double)(v * y) / N));
                    W_imag = -sin(2 * M_PI * ((double)(u * x) / N + (double)(v * y) / N));

                    sum_real += input[x][y] * W_real - input[x][y] * W_imag;
                    sum_imag += input[x][y] * W_imag + input[x][y] * W_real;
                }
            }

            output[u][v] = sqrt(sum_real * sum_real + sum_imag * sum_imag);
        }
    }
}

int main() {
    double input[N][N] = {
        {10, 20, 30, 40, 50, 60, 70, 80},
        {90, 100, 110, 120, 130, 140, 150, 160},
        {170, 180, 190, 200, 210, 220, 230, 240},
        {250, 260, 270, 280, 290, 300, 310, 320},
        {330, 340, 350, 360, 370, 380, 390, 400},
        {410, 420, 430, 440, 450, 460, 470, 480},
        {490, 500, 510, 520, 530, 540, 550, 560},
        {570, 580, 590, 600, 610, 620, 630, 640}
    };
    double output[N][N];

    DFT2D(input, output);

    int i, j;
    for (i = 0; i < N; i++) {
        for (j = 0; j < N; j++) {
            printf("%.2f ", output[i][j]);
        }
        printf("\n");
    }

    return 0;
}

该代码中的DFT2D函数实现了二维离散傅里叶变换，输入矩阵为input，输出矩阵为output。在主函数中，我们定义了一个8x8的输入矩阵，通过DFT2D函数进行变换，并输出结果。