光照效果

private const float BRIGHTNESS = 220.0F;
 Graphics g = this.pictureBox2.CreateGraphics();
            g.Clear(Color.White);
            Bitmap bmp = new Bitmap(this.pictureBox1.Image);
            int width = bmp.Width;
            int height = bmp.Height;

            Bitmap tmp = bmp.Clone(new RectangleF(0, 0, width, height), System.Drawing.Imaging.PixelFormat.DontCare);

            //发亮点右上角 此值会让强光中心发生偏移
            Point lightP = new Point(width - 40, height / 4);
            //R强光照射面的半径，即”光晕”
            int radius = Math.Min(width / 2 + 60, height / 2 + 60);

            for (int i = 1; i < width; i++)
                for (int j = 1; j < height; j++)
                {
                    float length = (float)Math.Sqrt(Math.Pow((i - lightP.X), 2) + Math.Pow((j - lightP.Y), 2));
                    //如果像素位于”光晕”之内
                    if (length < radius)
                    {
                        Color C = tmp.GetPixel(i, j);
                        int rV, gV, bV;
                        //亮度增加常量，该值越大，光亮度越强
                        float pixel = BRIGHTNESS * (1.0f - (length / radius));
                        rV = C.R + (int)pixel;
                        rV = Math.Max(0, Math.Min(rV, 255));
                        gV = C.G + (int)pixel;
                        gV = Math.Max(0, Math.Min(gV, 255));
                        bV = C.B + (int)pixel;
                        bV = Math.Max(0, Math.Min(bV, 255));
                        //将增亮后的像素值回写到位图
                        Color newC = Color.FromArgb(255, rV, gV, bV);
                        tmp.SetPixel(i, j, newC);
                    }
                }
            g.DrawImage(tmp, pictureBox2.ClientRectangle);// new Rectangle(0, 0, width, height)); 
　　　　　　　g.Dispose();