c语言实现灰度图转换

#include
#include
#include
#include 

#pragma pack(1)
typedef struct tagBITMAPFILEHEADER
{
    unsigned char bfType[2];//文件格式
    unsigned long bfSize;//文件大小
    unsigned short bfReserved1;//保留
    unsigned short bfReserved2;
    unsigned long bfOffBits; //DIB数据在文件中的偏移量
}fileHeader;
#pragma pack()


#pragma pack(1)
typedef struct tagBITMAPINFOHEADER
{
    unsigned long biSize;//该结构的大小
    long biWidth;//文件宽度
    long biHeight;//文件高度
    unsigned short biPlanes;//平面数
    unsigned short biBitCount;//颜色位数
    unsigned long biCompression;//压缩类型
    unsigned long biSizeImage;//DIB数据区大小
    long biXPixPerMeter;
    long biYPixPerMeter;
    unsigned long biClrUsed;//多少颜色索引表
    unsigned long biClrImporant;//多少重要颜色
}fileInfo;
#pragma pack()


#pragma pack(1)
typedef struct tagRGBQUAD
{
    unsigned char rgbBlue; //蓝色分量亮度
    unsigned char rgbGreen;//绿色分量亮度
    unsigned char rgbRed;//红色分量亮度
    unsigned char rgbReserved;
}rgbq;
#pragma pack()

int main()
{
    
    unsigned char ImgData[3000][3];
    
    unsigned char ImgData2[3000];
    
   
    int i, j, k;
    FILE* fpBMP, * fpGray;
    fileHeader* fh;
    fileInfo* fi;
    rgbq* fq;
    char filename1[20], filename2[20],filename3[20];
    errno_t error;
    printf("输入图像文件名：");
    scanf_s("%s", filename1,20);
    error = fopen_s(&fpBMP, filename1, "rb");
    if (error != 0)
    {
        printf("打开文件失败");
        exit(0);
    }
    printf("输出图像文件名：");
    scanf_s("%s", filename2,20);
    error = fopen_s(&fpGray, filename2, "wb");
    if (error != 0)
    {
        printf("创建文件失败");
        exit(0);
    }
    fh = (fileHeader*)malloc(sizeof(fileHeader));
    fi = (fileInfo*)malloc(sizeof(fileInfo));
    //读取位图头结构和信息头
    fread(fh, sizeof(fileHeader), 1, fpBMP);
    fread(fi, sizeof(fileInfo), 1, fpBMP);
    //修改头信息
    fi->biBitCount = 8;
    fi->biSizeImage = ((fi->biWidth * 3 + 3) / 4) * 4 * fi->biHeight;

    fh->bfOffBits = sizeof(fileHeader) + sizeof(fileInfo) + 256 * sizeof(rgbq);
    fh->bfSize = fh->bfOffBits + fi->biSizeImage;

    //创建调色版
    fq = (rgbq*)malloc(256 * sizeof(rgbq));
    for (i = 0; i < 256; i++)
    {
        fq[i].rgbBlue = fq[i].rgbGreen = fq[i].rgbRed = i;
        //fq[i].rgbReserved=0;
    }
    //将头信息写入
    fwrite(fh, sizeof(fileHeader), 1, fpGray);
    fwrite(fi, sizeof(fileInfo), 1, fpGray);
    fwrite(fq, sizeof(rgbq), 256, fpGray);
    //读取RGB图像素并转换为灰度值
    
 
    for (i = 0; i < fi->biHeight; i++)
    {
        for (j = 0; j < fi->biWidth; j++)
        {
            for (k = 0; k < 3; k++)
                fread(&ImgData[j][k], 1, 1, fpBMP);
        }
        for (j = 0; j < fi->biWidth; j++)
        {
            ImgData2[j] = int(((float)ImgData[j][0] +
                (float)ImgData[j][1] +
                (float)ImgData[j][2])/3);
            
        }
        //将灰度图信息写入
        fwrite(ImgData2, j, 1, fpGray);
        
    }
    
    free(fh);
    free(fi);
    free(fq);
    fclose(fpBMP);
    fclose(fpGray);
    printf("successn");
    return 0;
}

运行示例：
输入：
输出：