方法自身实现异部调用和WinForm上图片切换效果

以下的代码图片的切换效果已经出来了，但是奇慢无比，本来打算在循环内部加入"Thread.Sleep(n);"，但是不用加也很慢。看来C#实现漂亮的图片切换效果我是不行了，希望那位前辈给帮一下忙。

 private void SwitchImage(PictureBox pb,Image img,bool isAsync) {
            //异步调用
            if (isAsync) {
                Thread t = new Thread(delegate(object o) {
                                        SwitchImage((PictureBox)(((System.Collections.Stack)o).Pop()),
                                                    (Image)(((System.Collections.Stack)o).Pop()),
                                                    (bool)(((System.Collections.Stack)o).Pop())
                                                    );
                                      });
                System.Collections.Stack st = new System.Collections.Stack(3);
                st.Push(false);
                st.Push(img);
                st.Push(pb);
                t.Start(st);
                return;
            }

            float opacity = 0;
            float[][] nArray ={ new float[] {1, 0, 0, 0, 0}, 
                                new float[] {0, 1, 0, 0, 0}, 
                                new float[] {0, 0, 1, 0, 0}, 
                                new float[] {0, 0, 0, opacity, 0}, 
                                new float[] {0, 0, 0, 0, 1}
                               };
            
            while (opacity < 1){
                opacity += 0.1F;
                nArray[3][3] = opacity;
                ColorMatrix matrix = new ColorMatrix(nArray);
                ImageAttributes attributes = new ImageAttributes();
                attributes.SetColorMatrix(matrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
                Bitmap resultImage = new Bitmap(img.Width, img.Height);
                Graphics g = Graphics.FromImage(resultImage);
                g.DrawImage(img, new Rectangle(0, 0, img.Width, img.Height), 0, 0, img.Width, img.Height, GraphicsUnit.Pixel, attributes);
                pb.Image = resultImage;
                //Thread.Sleep(100);
            }
        }