怎么高效率的实现图片负片处理

        /// <summary>
        /// 反色，即底片效果
        /// </summary>
        /// <param name="imgIn">输入的源图片</param>
        /// <returns>处理后的图片</returns>
        public static Image Negative(Image imgIn)
        {

            if (null == imgIn)
                throw new Exception();

            int iHeight = imgIn.Height;
            int iWidth = imgIn.Width;

            Bitmap newBitmap = new Bitmap(iWidth, iHeight);
            Bitmap oldBitmap = imgIn as Bitmap;

            try
            {
                Color pixel;//表示一个像素点

                for (int x = 1; x < iWidth; x++)
                {
                    for (int y = 1; y < iHeight; y++)
                    {
                        int r, g, b;//分别表示一个像素点红，绿，蓝的分量。

                        pixel = oldBitmap.GetPixel(x, y);

                        r = 255 - pixel.R;
                        g = 255 - pixel.G;
                        b = 255 - pixel.B;

                        newBitmap.SetPixel(x, y, Color.FromArgb(pixel.A,r, g, b));
                    }
                }
            }
            catch (Exception ee)
            {
                throw new Exception();
            }
            return newBitmap;
        }