int M=pDoc->biHeader.biHeight;

     int N=pDoc->biHeader.biWidth;

           //double t1,t2;

           int t0;

           int tong1,tong2;

           int m,n,n1,n2;

           int L=255;

           //BYTE X[1000][1000];

           t0=L/2;

           while(1)

           { tong1=tong2=0;

             n1=n2=0;

       for(m=0;m<M;m++)

                    for(n=0;n<N;n++)

                              if(pDoc->Data[m][n]<t0)

                              { tong1+=pDoc->Data[m][n];n1++;}

                 else {tong2+=pDoc->Data[m][n];n2++;}

               if(tong1/n1+tong2/n2==2*t0)

      break;

                    t0=(tong1/n1+tong2/n2)/2;

           }

          for(m=0;m<M;m++)

                   for(n=0;n<N;n++)

                             if(pDoc->Data[m][n]<t0)

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

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

          Invalidate();

          }