C＃中如何使用图形路径，使光滑的圆弧区域 [英] c# How to make smooth arc region using graphics path

问题描述

我试图与圆边一个标签控件。
这是我在OnPaint（）方法，从标签继承MyClass的覆盖方法的代码。

I'm trying to make a label control with rounded sides. Here is my code in OnPaint() overridden method in myclass inherited from Label.

protected override void OnPaint(PaintEventArgs e)
    {
        e.Graphics.InterpolationMode = InterpolationMode.HighQualityBilinear;
        e.Graphics.CompositingQuality = CompositingQuality.HighQuality;
        e.Graphics.PixelOffsetMode = PixelOffsetMode.HighQuality;
        e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;

        LinearGradientBrush brush = new LinearGradientBrush(this.ClientRectangle, GradientColor1, GradientColor2, 90);
        e.Graphics.FillRectangle(brush, new Rectangle(new Point(0, 0), new Size(this.Width, this.Height)));

        using (GraphicsPath gp = new GraphicsPath())
        {
            gp.AddArc(new Rectangle(new Point(0, 0), new Size(this.Height, this.Height)), 90, 180);
            gp.AddLine(new Point(this.Height / 2, 0), new Point(this.Width - (this.Height / 2), 0));
            gp.AddArc(new Rectangle(new Point(this.Width - this.Height, 0), new Size(this.Height, this.Height)), -90, 180);
            gp.CloseFigure();

            this.Region = new Region(gp);
        }

        base.OnPaint(e);
    }

的问题是，它不平滑两侧的曲线与示出毛刺。
这里是控制的截图：

The problem is that it is not smoothing the curve on the sides and showing the glitches. Here is the screenshot of the control :

的

推荐答案

由于在评论中指出，你不能抗混叠的区域，所以你必须使用图形的FillPath方法，以便进行抗锯齿绘图

As stated in the comments, you can't anti-alias the region, so you have to use graphic's FillPath method in order for the drawing to be anti-aliased

protected override void OnPaint(PaintEventArgs e)
        {
            e.Graphics.InterpolationMode = InterpolationMode.HighQualityBilinear;
            e.Graphics.CompositingQuality = CompositingQuality.HighQuality;
            e.Graphics.PixelOffsetMode = PixelOffsetMode.HighQuality;
            e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;

            LinearGradientBrush brush = new LinearGradientBrush(this.ClientRectangle, Color.Aqua, Color.Blue, 90);

            using (GraphicsPath gp = new GraphicsPath())
            {
                gp.AddArc(new Rectangle(new Point(0, 0), new Size(this.Height, this.Height)), 90, 180);
                gp.AddLine(new Point(this.Height / 2, 0), new Point(this.Width - (this.Height / 2), 0));
                gp.AddArc(new Rectangle(new Point(this.Width - this.Height, 0), new Size(this.Height, this.Height)), -90, 180);
                gp.CloseFigure();

                e.Graphics.FillPath(brush, gp);
            }

            base.OnPaint(e);
        }

如果你真的需要改变我猜的区域，你将不得不使用一个稍微大一点的区域，然后一个用于图：

If you really need to change the region I guess you would have to use a slightly bigger region then the one used for the drawing:

protected override void OnPaint(PaintEventArgs e)
    {
        e.Graphics.InterpolationMode = InterpolationMode.HighQualityBilinear;
        e.Graphics.CompositingQuality = CompositingQuality.HighQuality;
        e.Graphics.PixelOffsetMode = PixelOffsetMode.HighQuality;
        e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;

        LinearGradientBrush brush = new LinearGradientBrush(this.ClientRectangle, Color.Aqua, Color.Blue, 90);

        using (GraphicsPath gp = new GraphicsPath())
        {
            AddRoundedRectangle(gp, new Point(1, 1), new Size(this.Size.Width - 2, Size.Height - 2));
            e.Graphics.FillPath(brush, gp);
        }

        using (GraphicsPath gp = new GraphicsPath())
        {
            AddRoundedRectangle(gp, new Point(0, 0), this.Size);
            this.Region = new Region(gp);
        }

        base.OnPaint(e);
    }

    private void AddRoundedRectangle(GraphicsPath gp, Point upperLeft, Size size)
    {
        gp.AddArc(new Rectangle(upperLeft, new Size(size.Height, size.Height)), 90, 180);
        gp.AddLine(new Point(size.Height / 2 , upperLeft.Y), new Point(size.Width - (size.Height / 2), upperLeft.Y));
        gp.AddArc(new Rectangle(new Point(size.Width - size.Height, upperLeft.Y), new Size(size.Height, size.Height)), -90, 180);
        gp.CloseFigure();
    }

第二个选项影响像MouseHover事件的优势，但可能会遇到问题你看到这个地区的边界。

The second option has the advantage of affecting events like MouseHover but may run into problems of you seeing the region's "border".

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