写一下Sobel边缘检测算子对图像进行边缘检测运算的c程序代码。要求目标图像为灰度图像。

以下是使用Sobel边缘检测算子对灰度图像进行边缘检测的C代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include "bmpfile.h"

#define PI 3.14159265358979323846

void sobel_edge_detection(unsigned char *src, unsigned char *dst, int width, int height)
{
    int i, j, k, gx, gy, sum;
    int sobel_x[3][3] = {{-1, 0, 1}, {-2, 0, 2}, {-1, 0, 1}};
    int sobel_y[3][3] = {{-1, -2, -1}, {0, 0, 0}, {1, 2, 1}};

    // 对图像进行边缘检测
    for (i = 1; i < height-1; i++) {
        for (j = 1; j < width-1; j++) {
            gx = gy = 0;
            for (k = 0; k < 3; k++) {
                gx += src[(i-1)*width+(j-1+k)] * sobel_x[0][k];
                gx += src[(i+1)*width+(j-1+k)] * sobel_x[2][k];
                gy += src[(i-1)*width+(j-1+k)] * sobel_y[0][k];
                gy += src[(i+1)*width+(j-1+k)] * sobel_y[2][k];
            }
            gx += src[i*width+(j-1)] * sobel_x[1][0];
            gx += src[i*width+(j+1)] * sobel_x[1][2];
            gy += src[i*width+(j-1)] * sobel_y[1][0];
            gy += src[i*width+(j+1)] * sobel_y[1][2];
            sum = abs(gx) + abs(gy);
            sum = sum > 255 ? 255 : sum;
            dst[i*width+j] = 255 - sum;
        }
    }
}

int main()
{
    BMPFILEHEADER header;
    BMPINFOHEADER info;
    unsigned char *src, *dst;
    int width, height, size;
    FILE *fp;

    // 读入BMP图像
    fp = fopen("image.bmp", "rb");
    fread(&header, sizeof(header), 1, fp);
    fread(&info, sizeof(info), 1, fp);
    width = info.biWidth;
    height = info.biHeight;
    size = width * height;
    src = (unsigned char*)malloc(size);
    dst = (unsigned char*)malloc(size);
    fread(src, sizeof(unsigned char), size, fp);
    fclose(fp);

    // 对图像进行边缘检测
    sobel_edge_detection(src, dst, width, height);

    // 将结果保存为BMP图像
    fp = fopen("result.bmp", "wb");
    fwrite(&header, sizeof(header), 1, fp);
    fwrite(&info, sizeof(info), 1, fp);
    fwrite(dst, sizeof(unsigned char), size, fp);
    fclose(fp);

    // 释放内存
    free(src);
    free(dst);

    return 0;
}

其中，`sobel_edge_detection()`函数用于对图像进行边缘检测，使用了Sobel算子计算水平方向和竖直方向上的梯度，并将边缘强度计算为两个方向上的梯度的绝对值之和，最终得到边缘检测结果。