c++图像处理：24位真彩图颜色变换

#include<iostream>
#include<Windows.h>
using namespace std;

bool isred(BYTE r,BYTE g,byte b){
if(r>g&&r>b) return true;
else return false;
}
void red2green(BYTE& r,BYTE& g,BYTE& b){
BYTE tmp=r;
r=g;
g=tmp;
}

int main(){
FILE *fpin=fopen("flo.bmp","rb+");
if(fpin==NULL){
cout<<"目录里没有输入图"<<endl;
system("pause");
return 0;
}
BITMAPFILEHEADER bitmapfileheader;
BITMAPINFOHEADER bitmapinfoheader;
fread(&bitmapfileheader,sizeof(bitmapfileheader),1,fpin);
fread(&bitmapinfoheader,sizeof(bitmapinfoheader),1,fpin);

if(bitmapfileheader.bfType!='B'+'M'*256){
cout<<"不是bmp格式"<<endl;
fclose(fpin);
system("pause");
return 0;
}
if(bitmapinfoheader.biBitCount!=24){
cout<<"不是24位bmp"<<endl;
fclose(fpin);
system("pause");
return 0;
}

//设置fpout
FILE *fpout=fopen("output.bmp","wb+");

//BITMAPFILEHEADER bitmapfileheader2;
//BITMAPINFOHEADER bitmapinfoheader2;
//bitmapfileheader2=bitmapfileheader;
//bitmapinfoheader2=bitmapinfoheader;
fwrite(&bitmapfileheader,sizeof(bitmapfileheader),1,fpout);
fwrite(&bitmapinfoheader,sizeof(bitmapinfoheader),1,fpout);

if(bitmapinfoheader.biClrUsed!=0){
cout<<"是索引图"<<endl;
system("pause");
return 0;
}
if(bitmapinfoheader.biBitCount==24){
cout<<"24位真彩图"<<endl;
//int line_width=((bitmapinfoheader.biWidth*bitmapinfoheader.biBitCount+24)/32)*4;
int line_width=bitmapinfoheader.biWidth*3;
BYTE *line_buf=new BYTE[line_width];
for(int i=0;i<bitmapinfoheader.biHeight;i++){
fread(line_buf,line_width,1,fpin);
for(int j=0;j<bitmapinfoheader.biWidth;j++){
BYTE b=line_buf[3*j];
BYTE g=line_buf[3*j+1];
BYTE r=line_buf[3*j+2];
if(isred(r,g,b)){
red2green(line_buf[3*j+2],line_buf[3*j+1],line_buf[3*j]);
}
}
fwrite(line_buf,line_width,1,fpout);
}
fclose(fpin);
fclose(fpout);
delete []line_buf;
cout<<"红变绿完成"<<endl;
}

system("pause");
return 0;
}