c语言代码实现直方图均衡进行灰度变换的代码

下面是C语言代码实现直方图均衡进行灰度变换的代码：

#include <stdio.h>
#include <stdlib.h>
#define Gray_Level 256

// 直方图均衡化函数
void hist_equalization(unsigned char* img, int width, int height)
{
    int i, j, pixel_num, gray_sum;
    int gray_scale[Gray_Level] = {0};
    int gray_map[Gray_Level] = {0};

    // 计算每个灰度级的像素数量
    pixel_num = width * height;
    for (i = 0; i < pixel_num; i++) 
    {
        gray_scale[*(img + i)]++;
    }

    // 计算每个灰度级新的映射值
    gray_sum = 0;
    for (i = 0; i < Gray_Level; i++) 
    {
        gray_sum += gray_scale[i];
        gray_map[i] = (int)(255.0 * gray_sum / pixel_num + 0.5);
    }

    // 对图像进行直方图均衡化
    for (i = 0; i < height; i++) 
    {
        for (j = 0; j < width; j++) 
        {
            *(img + i * width + j) = gray_map[*(img + i * width + j)];
        }
    }
}

int main()
{
    // 加载图像
    unsigned char* img = 0;
    int width, height;
    FILE* fp = fopen("lena.pgm", "rb");
    if (!fp) 
    {
        printf("Load image failed!");
        return -1;
    }
    fscanf(fp, "%*s %d %d %*d", &width, &height);
    img = (unsigned char*)malloc(sizeof(unsigned char) * width * height);
    fread(img, sizeof(unsigned char), width * height, fp);
    fclose(fp);

    // 对图像进行直方图均衡化
    hist_equalization(img, width, height);

    // 保存结果
    fp = fopen("lena_histeq.pgm", "wb");
    fprintf(fp, "P5\n%d %d\n%d\n", width, height, 255);
    fwrite(img, sizeof(unsigned char), width * height, fp);
    fclose(fp);

    // 释放内存
    free(img);

    return 0;
}