怎么将黑白图保存为单色位图

如何将黑白图保存为单色位图


在做一个项目，使用插件已经把数据转换成单色二维码图片，现在要把图片保存为单色BMP图（如上图所示，即保存好的图片查看颜色属性是显示黑白图，而不是彩色图）。请问保存的代码要怎样写？谢谢
------解决思路----------------------
不多说。在项目的属性里要勾选 容许不安全代码。

 public Bitmap ConvertTo24bppTo1bpp(Bitmap SrcImg)
        {
            unsafe
            {
                byte* SrcPointer, DestPointer;
                int Width, Height, SrcStride, DestStride;
                int X, Y, Index, Sum; ;
                Bitmap DestImg = new Bitmap(SrcImg.Width, SrcImg.Height, PixelFormat.Format1bppIndexed);
                BitmapData SrcData = new BitmapData();
                SrcImg.LockBits(new Rectangle(0, 0, SrcImg.Width, SrcImg.Height), ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb, SrcData);
                BitmapData DestData = new BitmapData();
                DestImg.LockBits(new Rectangle(0, 0, SrcImg.Width, SrcImg.Height), ImageLockMode.ReadWrite, PixelFormat.Format1bppIndexed, DestData);
                Width = SrcImg.Width; Height = SrcImg.Height; SrcStride = SrcData.Stride; DestStride = DestData.Stride;
                for (Y = 0; Y < Height; Y++)
                {
                    SrcPointer = (byte *)SrcData.Scan0 + Y * SrcStride;
                    DestPointer = (byte*)DestData.Scan0 + Y * DestStride;
                    Index = 7; Sum = 0;
                    for (X = 0; X < Width; X++)
                    {
                        if (*SrcPointer + (*(SrcPointer + 1) << 1) + *(SrcPointer + 2)>= 512) Sum += (1 << Index);
                        if (Index == 0)
                        {
                            *DestPointer = (byte)Sum;
                            Sum = 0;
                            Index = 7;
                            DestPointer++;
                        }
                        else
                            Index--;
                        SrcPointer+=3;
                    }
                    if (Index != 7) *DestPointer = (byte)Sum;
                }
                SrcImg.UnlockBits(SrcData);
                DestImg.UnlockBits(DestData);
                return DestImg;
            }
        }

然后再用GDI+的SAVE函数保存为BMP就可以了。