This paper analyzes the implementation code of C color image graying algorithm

        public static Bitmap MakeGrayscale(Bitmap original)
        {
            //create a blank bitmap the same size as original
            Bitmap newBitmap = new Bitmap(original.Width, original.Height);
            //get a graphics object from the new image
            Graphics g = Graphics.FromImage(newBitmap);
            //create the grayscale ColorMatrix
            System.Drawing.Imaging.ColorMatrix colorMatrix = new System.Drawing.Imaging.ColorMatrix(
               new float[][] 
              {
                 new float[] {.3f, .3f, .3f, 0, 0},
                 new float[] {.59f, .59f, .59f, 0, 0},
                 new float[] {.11f, .11f, .11f, 0, 0},
                 new float[] {0, 0, 0, 1, 0},
                 new float[] {0, 0, 0, 0, 1}
              });
            //create some image attributes
            System.Drawing.Imaging.ImageAttributes attributes = new System.Drawing.Imaging.ImageAttributes();
            //set the color matrix attribute
            attributes.SetColorMatrix(colorMatrix);
            //draw the original image on the new image
            //using the grayscale color matrix
            g.DrawImage(original, new Rectangle(0, 0, original.Width, original.Height),
               0, 0, original.Width, original.Height, GraphicsUnit.Pixel, attributes);
            //dispose the Graphics object
            g.Dispose();
            return newBitmap;
        }