//Loading original bitmap.
Aurigma.GraphicsMill.Bitmap bmp = new Aurigma.GraphicsMill.Bitmap(@"y:\venezia_01s.bmp");

//Converting to 8bppGrayscale to discard color information as we don't need it
bmp.ColorManagement.Convert(Aurigma.GraphicsMill.PixelFormat.Format8bppGrayScale);

//Building look up table (LUT) for our grayscale image. It specifies black (0) result value for all
//pixels in the range [0, 254]. And pure white pixels (255) remain white.
Aurigma.GraphicsMill.Transforms.Lut nonWhiteToBlackLut = new Aurigma.GraphicsMill.Transforms.Lut(false);
for (int i = 0; i <= 254; i++)
      nonWhiteToBlackLut[i] = 0;
nonWhiteToBlackLut[255] = 255;

//Applying LUT to obtain the desired result. After that you can do what you want
//with this image - save it, convert to 24bpp RGB or convert to 1bpp bitmap,
//according to your task.
bmp.ColorAdjustment.ApplyLut(nonWhiteToBlackLut);
bmp.Save(@"y:/whiteAndBlackResult.bmp");