我用VC++写的一个给不规则推行填充颜色的程序，能够正常运行，但是在填充后没有任何颜色显示，把颜色改了很多次也不行！！下面是代码,麻烦高手知道下：
CDC*pDC=GetDC();
    int i,n=6;
    CPoint B[6]={CPoint(30,180),CPoint(30,390),CPoint(210,240),CPoint(390,360),CPoint(390,210),CPoint(180,30)};
    int xmax=B[0].x,ymax=B[0].y,xmin=B[0].x,ymin=B[0].y;

        for(i=1;i<=n;i++)
    {
        if(xmin>B[i].x)
            xmin=B[i].x;
        if(xmax<B[i].x)
            xmax=B[i].x;
        if(ymin>B[i].y)
            ymin=B[i].y;
        if(ymax<B[i].y)
            ymax=B[i].y;
    }
    pDC->MoveTo(B[0]);
    for(i=1;i<=n;i++)
    {
        pDC->LineTo(B[i%n]);
        
    }
   
    int a,m=4,x,y,flag,C1=(50,50,50),C2=RGB(255,50,250);
    CPoint C[4]={CPoint(xmin,ymin),CPoint(xmin,ymax),CPoint(xmax+30,ymax),CPoint(xmax+30,ymin)};
    pDC->MoveTo(C[0]);
    for(a=1;a<=m;a++)
    {
        pDC->LineTo(C[a%m]);
        
    }
    for(y=ymin;y<=ymax;y++)
    {
        flag=-1;
        for(x=xmin;x<=xmax;x++)
        {
            if(pDC->GetPixel(x-1,y)==C1)
                flag=-flag;
            if(flag==1)
            pDC->SetPixel(x,y,C2);
        }
    }