C语言实现BMP格式图片转化为灰度

本文实例为大家分享了c语言将bmp格式图片转化为灰度的具体代码，供大家参考，具体内容如下

代码如下：

#include<stdio.h>
#include<malloc.h>
#include<stdlib.h>
 
 
#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()
/*
位图数据信息结构
*/
#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()
/*
调色板结构
*/
#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()
{
    file *fp1 = fopen("c:\\users\\administrator\\desktop\\data\\bmp\\image.bmp", "rb+");
    if (fp1 == null)
    {
        printf("打开文件fp1失败");
        exit(0);
    }
 
    file *fp2 = fopen("c:\\users\\administrator\\desktop\\data\\bmp\\imagegray.bmp", "wb");
    if (fp1 == null)
    {
        printf("打开文件fp2失败");
        exit(0);
    }
 
    fileheader * fh;
    fileinfo * fi;
    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, fp1);
    fread(fi, sizeof(fileinfo), 1, fp1);
 
    printf("\\\\\\\\\\\\\\\\\\\\原始图片信息\\\\\\\\\\\\\\\\\\\\\\\\\\\n");
    printf("bmp文件头：\n");
    printf("bfsize:%d\n", fh->bfsize);
    printf("bfoffbits:%d\n", fh->bfoffbits);
    printf("\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\n");
    printf("bmp信息头\n");
    printf("结构体长度：%d \n", fi->bisize);
    printf("位图宽度：%d \n", fi->biwidth);
    printf("位图高度：%d \n", fi->biheight);
    printf("位图平面数：%d \n", fi->biplanes);
    printf("颜色位数：%d \n", fi->bibitcount);
    printf("压缩方式：%d \n", fi->bicompression);
    printf("实际位图数据占用的字节数：%d \n", fi->bisizeimage);
    printf("x方向分辨率：%d \n", fi->bixpixpermeter);
    printf("y方向分辨率：%d \n", fi->biypixpermeter);
    printf("使用的颜色数：%d \n", fi->biclrused);
    printf("重要颜色数：%d \n", fi->biclrimporant);
    printf("\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\n");
 
    //修改信息头
    fi->bibitcount = 8;
    //fi->bisizeimage = ((fi->biwidth * 3 + 3) / 4) * 4 * fi->biheight;
    fi->bisizeimage = fi->biheight*fi->biwidth;
    //修改文件头
    fh->bfoffbits = sizeof(fileheader) + sizeof(fileinfo) + 256 * sizeof(rgbq);
    fh->bfsize = fh->bfoffbits + fi->bisizeimage;
 
    printf("\\\\\\\\\\\\\\\\\\\\修改后的图片信息\\\\\\\\\\\\\\\\\\\\\\\\\\\n");
    printf("bmp文件头：\n");
    printf("bfsize:%d\n", fh->bfsize);
    printf("bfoffbits:%d\n", fh->bfoffbits);
    printf("\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\n");
    printf("bmp信息头\n");
    printf("结构体长度：%d \n", fi->bisize);
    printf("位图宽度：%d \n", fi->biwidth);
    printf("位图高度：%d \n", fi->biheight);
    printf("位图平面数：%d \n", fi->biplanes);
    printf("颜色位数：%d \n", fi->bibitcount);
    printf("压缩方式：%d \n", fi->bicompression);
    printf("实际位图数据占用的字节数：%d \n", fi->bisizeimage);
    printf("x方向分辨率：%d \n", fi->bixpixpermeter);
    printf("y方向分辨率：%d \n", fi->biypixpermeter);
    printf("使用的颜色数：%d \n", fi->biclrused);
    printf("重要颜色数：%d \n", fi->biclrimporant);
    printf("\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\n");
 
    //创建调色板
    int i,j,k=0;
    rgbq *fq = (rgbq *)malloc(256 * sizeof(rgbq));
    for (i = 0; i<256; i++)
    {
        fq[i].rgbblue = fq[i].rgbgreen = fq[i].rgbred = i;
    }
    //写入文件头、信息头、调色板
    fwrite(fh, sizeof(fileheader), 1, fp2);
    fwrite(fi, sizeof(fileinfo), 1, fp2);
    fwrite(fq, sizeof(rgbq), 256, fp2);
 
    //将位图信息转为灰度
    //存储bmp一行的像素点
    //unsigned char imgdata[900][3];
    unsigned char imgdata[3000][3];
    //将灰度图像存到一维数组中
    //unsigned char graydata2[900];
    unsigned char imgdata2[3000];
    /*
    //错误的算法
    for (i = 0; i < fi->biheight; i++)
    {
        for (j = 0; j < (fi->biwidth * 3 + 3) / 4 * 4; j++)
        {
            for (k = 0; k < 3; k++)
            {
                fread(&imgdata[j][k], 1, 1, fp1);
            }
        }
        for (j = 0; j < (fi->biwidth + 3) / 4 * 4; j++)
        {
            imgdata2[j] = int((float)imgdata[j][0] * 0.114 +
                (float)imgdata[j][1] * 0.587 +
                (float)imgdata[j][2] * 0.299);
        }
        //将灰度图信息写入
        fwrite(imgdata2, j, 1, fp2);
    }
    */
    /*
    //正确的算法(1)
    for (i = 0; i<fi->biheight; i++)
    {
        for (j = 0; j<(fi->biwidth + 3) / 4 * 4; j++)
        {
            for (k = 0; k<3; k++)
            fread(&imgdata[j][k], 1, 1, fp1);
        }
        for (j = 0; j<(fi->biwidth + 3) / 4 * 4; j++)
        {
            imgdata2[j] = int((float)imgdata[j][0] * 0.114 +
                (float)imgdata[j][1] * 0.587 +
                (float)imgdata[j][2] * 0.299);
        }
        //将灰度图信息写入
        fwrite(imgdata2, j, 1, fp2);
    }
    */
    //正确算法（2）
    unsigned char * * bmp_data;
    bmp_data = new unsigned char*[fi->biheight]; //声明一个指针数组
    unsigned char *data288 = new unsigned char[fi->biheight*fi->biwidth];
 
    for (i = 0; i<fi->biheight; i++)
        bmp_data[i] = new unsigned char[(fi->biwidth * 3 + 3) / 4 * 4]; //每个数组元素也是一个指针数组
    for (i = 0; i<fi->biheight; i++)
        for (j = 0; j<(fi->biwidth * 3 + 3) / 4 * 4; j++)
            fread(&bmp_data[i][j], 1, 1, fp1);//每次只读取一个字节，存入数组
 
    for (i = 0; i<fi->biheight; i++)//将24位真彩色转换成灰度图
        for (j = 0; j<fi->biwidth; j++){
        data288[fi->biwidth*i + j] = ((unsigned char)((float)bmp_data[i][3 * j] * 0.114 + (float)bmp_data[i][3 * j + 1] * 0.587 + (float)bmp_data[i][3 * j + 2] * 0.299));
        }
 
    fwrite(data288, fi->bisizeimage, 1, fp2);
    free(fh);
    free(fi);
    free(fq);
    fclose(fp1);
    fclose(fp2);
    printf("success\n");
    return 0;
}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。