#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;
}