C# DrawImage 使用 DoubleBuffered 不工作

Question

您好，我有一个覆盖 OnPaint 方法的 c# 用户控件。

在我的 OnPaint 方法中，我有以下代码：

// Draw the new button. 
protected override void OnPaint(PaintEventArgs e) {
    Color btnColor = this.ButtonColor;
    if (!this.ButtonEnabled) {
        btnColor = Color.LightGray;
    }


    Bitmap GraphicsImage = new Bitmap(24, 24, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
    Graphics.FromImage(GraphicsImage).Clear(btnColor);

    Graphics graphics = e.Graphics;
    SolidBrush myBrush = new SolidBrush(btnColor);
    Pen myPen = new Pen(btnColor);
    // Draw the button in the form of a circle
    graphics.DrawEllipse(myPen, 0, 0, 40, 40);
    graphics.FillEllipse(myBrush, new Rectangle(0, 0, 40, 40));



    if (!DesignMode) {
        Image iconImg = null;

        switch (this.ButtonImage) {
            case CircleButtonImage.ArrowDown:
                iconImg = POS.Framework.Utility.Common.GetResourceImage("arrowdown_16.png");
                break;
            case CircleButtonImage.ArrowUp:
                iconImg = POS.Framework.Utility.Common.GetResourceImage("arrowup_16.png");
                break;
            case CircleButtonImage.Cross:
                iconImg = POS.Framework.Utility.Common.GetResourceImage("close_16.png");
                break;
            case CircleButtonImage.Plus:
                iconImg = POS.Framework.Utility.Common.GetResourceImage("plus_16.png");
                break;
        }


        graphics = Graphics.FromImage(GraphicsImage);
        graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
        graphics.DrawImage(iconImg, 5, 5);

        this.CreateGraphics().DrawImageUnscaled(GraphicsImage, new Point(7, 6));

    }


    myBrush.Dispose();
    myPen.Dispose();
}

这很好用，但为了避免闪烁，我在我的构造函数中添加了：

 this.SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.UserPaint | ControlStyles.DoubleBuffer, true);

然后 png 图像不再显示。

没有双缓冲：

双缓冲：

Any clue on how to fix this. I want to avoid flickering but need the image to be rendered.

Answer 1

不要使用 CreateGraphics。您需要使用的 Graphics 对象作为参数传递给 OnPaint，在 PaintEventArgs.

中

另外，你真的应该自己清理一下：

using (var graphics = Graphics.FromImage(GraphicsImage))
{
  graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
  graphics.DrawImage(iconImg, 5, 5);
}

GDI+ 对象是非常有限的资源 :) 除此之外，SmoothingMode 对您在这里所做的事情几乎没有用处 - 至少阅读文档而不是仅仅阅读货物确实有帮助。

C# DrawImage 使用 DoubleBuffered 不工作

C# DrawImage using DoubleBuffered not working

c#

onpaint

winforms