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);
            }
        }