爲什麼渲染車削黑色

Question

我正在使用眼動儀在窗體上顯示眼球運動。這些動作一直閃爍很多，所以我發現我可以使用BufferedGraphics，除了眼動開始之外，它們都可以正常工作，它將窗體從原始顏色變成黑色。這是代碼。希望有人能幫助！

private void button2_Click(object sender, EventArgs e) 
{ 
    var host = new Host(); 
    var gazeStream = host.Streams.CreateGazePointDataStream(); 
    gazeStream.GazePoint((x, y, ts) 
     => drawCircle(new PointF((float)x, (float)y))); 
} 

delegate void SetCallback(PointF point); 

private void drawCircle(PointF point) 
{ 
    float x = point.X; 
    float y = point.Y; 

    if (this.InvokeRequired) 
    { 
     SetCallback d = new SetCallback(drawCircle); 
     this.Invoke(d, new object[] { point }); 
    } 
    else 
    { 
     SolidBrush semiTransBrush = new SolidBrush(Color.Coral); 
     Pen pen = new Pen(Color.Aquamarine, 2); 

     BufferedGraphicsContext currentContext; 
     BufferedGraphics myBuffer; 
     // Gets a reference to the current BufferedGraphicsContext 
     currentContext = BufferedGraphicsManager.Current; 
     // Creates a BufferedGraphics instance associated with Form1, and with 
     // dimensions the same size as the drawing surface of Form1. 
     myBuffer = currentContext.Allocate(this.CreateGraphics(),this.DisplayRectangle); 
     myBuffer.Graphics.DrawEllipse(pen, x, y, 100, 100); 
     myBuffer.Graphics.FillEllipse(semiTransBrush, x, y, 100, 100); 


     // Renders the contents of the buffer to the specified drawing surface. 
     myBuffer.Render(this.CreateGraphics()); 

     myBuffer.Dispose(); 
    } 

您可以在圖片中看到的圓圈顯示控件後面這似乎是形式沒有了嗎？

Answer 1

當您分配緩衝區時，它會使用您提供的圖形創建兼容的渲染表面。但它不會複製它或任何東西，所以如果你只畫一個圓圈，其餘部分仍然是黑色的。

BufferedGraphics真的可以幫助您避免在特殊情況下閃爍（例如，系統雙緩衝由於某種原因必須被禁用），但這裏這是一個矯枉過正。

所以關鍵只是啓用雙緩衝，並在Paint事件（或OnPaint方法）中執行每個繪製。在你的代碼中，你會立即進行繪製，它總是閃爍。相反，您應該使表單失效，並讓系統執行定期重繪會話，如果您願意，可以使用雙重緩衝。

到構造函數：

SetStyle(ControlStyles.OptimizedDoubleBuffer | ControlStyles.DoubleBuffer | ControlStyles.AllPaintingInWmPaint, true); 

然後修改Click事件：

private PointF lastGazePoint; 

private void button2_Click(object sender, EventArgs e) 
{ 
    var host = new Host(); 
    var gazeStream = host.Streams.CreateGazePointDataStream(); 
    gazeStream.GazePoint((x, y, ts) => 
     { 
      lastGazePoint = new PointF((float)x, (float)y); 
      Invalidate(); 
     }); 
} 

繪畫本身：

protected override void OnPaint(PaintEventArgs e) 
{ 
    base.OnPaint(e); 
    DrawCircle(e.Graphics, lastGazePoint.X, lastGazePoint.Y); 
} 

最後，修改DrawCircle使用來自PaintEventArgs的Graphics ：

private void DrawCircle(Graphics g, float x, float y) 
{ 
    using (Brush semiTransBrush = new SolidBrush(Color.Coral)) 
    { 
     using (Pen pen = new Pen(Color.Aquamarine, 2)) 
     { 
      g.DrawEllipse(pen, x, y, 100, 100); 
      g.FillEllipse(semiTransBrush, x, y, 100, 100); 
     }   
    }   
}