怎樣用VC++實現位圖的灰度化

img.Load(_T("d:\\sex.bmp"));

COLORREF?p;

int?r,g,b,avg;

int?width=img.GetWidth();

int?height=img.GetHeight();

for(int?x=0;x<width;x++)

{

for(int?y=0;y<height;y++)

{

p=img.GetPixel(x,y);

r=GetRValue(p);

g=GetGValue(p);

b=GetBValue(p);

avg=(r+g+b)/3;

img.SetPixelRGB(x,y,avg,avg,avg);

}

}

img.Draw(GetDC()->m_hDC,CRect(0,0,width,height));