int M=pDoc->biHeader.biHeight;

     int N=pDoc->biHeader.biWidth;

           int t1=80,t2=160;

           int tong1=0,tong2=0,tong3=0;

           int m,n,n1=0,n2=0,n3=0;

           //BYTE X[1000][1000];

    for(m=0;m<M;m++)

                    for(n=0;n<N;n++)

                              if(pDoc->Data[m][n]<t1)

                              { tong1+=pDoc->Data[m][n];

                                n1++;

                              }

                   else if(pDoc->Data[m][n]<t2)

                   {tong2+=pDoc->Data[m][n];

                     n2++;

                   }

                   else

                   { tong3+=pDoc->Data[m][n];

                      n3++;

                   }                

          for(m=0;m<M;m++)

                   for(n=0;n<N;n++)

                             if(pDoc->Data[m][n]<t1)

                                      pDoc->Data[m][n]=tong1/n1;

                   else if(pDoc->Data[m][n]<t2)

                                 pDoc->Data[m][n]=tong2/n2;

                   else pDoc->Data[m][n]=tong3/n3;

          Invalidate();

}