CImage::SetPixel崩溃

CImage image;
byte r, g, b;
unsigned short buf;

            for (int j = 0; j < 256; j++)
            {
                for (int i = 0; i < 336; i++)
                {
                    buf = dealingImageDataBuf[j * 336 * 2 + i * 2 + 1];
                    buf <<= 8;
                    buf += dealingImageDataBuf[j * 336 * 2 + i * 2];

// buf = dealingImageDataBuf[j * 336 * 2 + i * 2];
// buf <<= 8;
// buf += dealingImageDataBuf[j * 336 * 2 + i * 2 + 1];

                    r = (byte)(buf >> 6);
                    g = (byte)(r);
                    b = (byte)(r);

                    COLORREF color = RGB(r,g,b);

                    image.SetPixel(i, j, color);
                }
            }


            运行到此处崩溃，expression:m_hBitmap != 0

image没有初始化，dealingImageDataBuf再哪里定义的，是否下标越界。
buf += dealingImageDataBuf[j * 336 * 2 + i * 2];而buf只是一个short，它也许会溢出。