【转】真彩bmp图像转化为灰度图

感谢大神分享 原链接https://blog.csdn.net/u011450295/article/details/37316909

下面是用c语言实现的将 真彩 bmp图像 转化为灰度图。

#include "stdafx.h"
#include
#include

int _tmain(int argc, _TCHAR* argv[])
{
    int bmpHeight;
    int bmpWidth;
    unsigned char *pBmpBuf;
    RGBQUAD *pColorTable;
    int biBitCount;

    //读取bmp文件
    FILE *fp=fopen("dog1.bmp","rb");
    if(fp==0)
        return 0;
    fseek(fp,sizeof(BITMAPFILEHEADER),0);

    BITMAPINFOHEADER head;
    fread(&head,40,1,fp);
    bmpHeight=head.biHeight;
    bmpWidth=head.biWidth;
    biBitCount=head.biBitCount;

    if(biBitCount==8)
    {
        pColorTable=new RGBQUAD[256];
        fread(pColorTable,sizeof(RGBQUAD),256,fp);
    }
    int LineByte=(bmpWidth*biBitCount/8+3)/4*4;//保证每一行字节数都为4的整数倍
    pBmpBuf=new unsigned char[LineByte*bmpHeight];
    fread(pBmpBuf,LineByte*bmpHeight,1,fp);
    fclose(fp);
    测试读取功能模块
    printf("bmpWidth:%d ,bmpHeight: %d,biBitCount:%d \n",bmpWidth,bmpHeight,biBitCount);

    //将24位真彩图灰度化并保存

    FILE *fp1=fopen("dog2.bmp","wb");
    if(fp1==0)
        return 0;
    int LineByte1=(bmpWidth*8/8+3)/4*4;
    //修改文件头,其中有两项需要修改，分别为bfSize和bfOffBits
    BITMAPFILEHEADER bfhead;
    bfhead.bfType=0x4D42;
    bfhead.bfSize=14+40+256*sizeof(RGBQUAD)+LineByte1*bmpHeight;//修改文件大小
    bfhead.bfReserved1=0;
    bfhead.bfReserved2=0;
    bfhead.bfOffBits=14+40+256*sizeof(RGBQUAD);//修改偏移字节数
    fwrite(&bfhead,14,1,fp1);    //将修改后的文件头存入fp1；

    //修改信息头，其中有两项需要修改，1个位biBitCount:真彩图为24 ，应改成8；另一个是biSizeImage:由于每像素所占位数的变化，所以位图数据的大小发生变化
    BITMAPINFOHEADER head1;
    head1.biBitCount=8;    //将每像素的位数改为8
    head1.biClrImportant=0;
    head1.biCompression=0;
    head1.biClrUsed=0;
    head1.biHeight=bmpHeight;
    head1.biWidth=bmpWidth;
    head1.biPlanes=1;
    head1.biSize=40;
    head1.biSizeImage=LineByte1*bmpHeight;//修改位图数据的大小
    head1.biXPelsPerMeter=0;
    head1.biYPelsPerMeter=0;
    fwrite(&head1,40,1,fp1);  //将修改后的信息头存入fp1;

    if(biBitCount==24)//判断是否是真彩图，若是，由于真彩图没有颜色表，所以在变为灰度图后要加上颜色表
    {
        pColorTable=new RGBQUAD[256];
        for (int  i = 0; i < 256; i++ )
            pColorTable[i].rgbRed = pColorTable[i].rgbGreen = pColorTable[i].rgbBlue = i; //是颜色表里的B、G、R分量都相等，且等于索引值

    }
    fwrite(pColorTable,sizeof(RGBQUAD),256,fp1); //将颜色表写入fp1;

    //写位图数据
    unsigned char *pBmpBuf1;
    pBmpBuf1= new unsigned char[LineByte1*bmpHeight];
    for(int i=0;i
        for(int j=0;j
        {
            unsigned char *pb1,*pb2;
            pb1=pBmpBuf+i*LineByte+j*3;
            int y=*(pb1)*0.299+*(pb1+1)*0.587+*(pb1+2)*0.114;   //将每一个像素都按公式y=B*0.299+G*0.587+R*0.114进行转化
            pb2=pBmpBuf1+i*LineByte1+j;
            *pb2=y;

        }
    if(biBitCount==8)
        fwrite(pBmpBuf,LineByte*bmpHeight,1,fp1);
    else
        fwrite(pBmpBuf1,LineByte1*bmpHeight,1,fp1);


    fclose(fp1);

    system("pause");
    return 0;
}