黑白效果

 Bitmap bmp = new Bitmap(pictureBox1.Image); 
            int height = bmp.Height;
            int width = bmp.Width; 
            Bitmap tmp = new Bitmap(width, height);
            Color c;
            int r, g, b, Result = 0; 
            for (int i = 0; i < width; i++)
                for (int j = 0; j < height; j++)
                {
                    c = bmp.GetPixel(i, j);
                    r = c.R;
                    g = c.G;
                    b = c.B;
                    //以加权平均值法产生黑白图像 
                    Result = ((int)(0.7 * r) + (int)(0.2 * g) + (int)(0.1 * b));
                    tmp.SetPixel(i, j, Color.FromArgb(Result, Result, Result));
                }
            this.pictureBox2.Image = tmp;