C# 从图形转换为位图时为空位图

我使用一个库从这里绘制大纲文本

我为测试amd编写了一个函数，试图将outlineText图形对象保存为位图 图形对象在控件上正确绘制，但当我将其保存为图像时，结果图像为空

        Graphics graphic = this .CreateGraphics();
        graphic.SmoothingMode = SmoothingMode.AntiAlias;
        StringFormat fmt = new StringFormat(StringFormat.GenericTypographic);
        Int32 lNum = (Int32)Math.Log((Double)this.TextAlign, 2);
        fmt.LineAlignment = (StringAlignment)(lNum / 4);
        fmt.Alignment = (StringAlignment)(lNum % 4);

        OutlineText m_OutlineText = new OutlineText();            

        m_OutlineText.EnableShadow(true);
        m_OutlineText.SetNullShadow();
        m_OutlineText.Shadow(ShadowColor, ShadowSize, new Point(4, 4));
        FontFamily fontFamily = this.Font.FontFamily;
        float fStartX = 0.0f;
        float fStartY = 0.0f;
        float fDestWidth = 0.0f;
        float fDestHeight = 0.0f;
        m_OutlineText.MeasureString(
            graphic,
            fontFamily,
            this.Font.Style,
            (int)this.Font.Size,
            this.Text,
            new Point(10, 10),
            fmt,
            ref fStartX,
            ref fStartY,
            ref fDestWidth,
            ref fDestHeight);

        LinearGradientBrush gradientBrush = new LinearGradientBrush(new RectangleF(fStartX, fStartY, fDestWidth - (fStartX - 10), fDestHeight - (fStartY - 10)),
           GrediantA, GrediantB, LinearGradientMode.Vertical);
        m_OutlineText.TextOutline(gradientBrush, OutlineColor, OutlineSize);
        if (_myRc == null)
        {
            _myRc = ClientRectangle;
        }
        m_OutlineText.DrawString(graphic, fontFamily, this.Font.Style, (int)this.Font.Size, this.Text, _myRc, fmt);


      _textImage = new Bitmap(this.Width, this.Height, graphic);
      _textImage.Save(@"C:\bmp.jpg");

构造函数：以指定的大小和指定图形对象的分辨率初始化位图类的新实例。它应该是空的。仅使用图形分辨率

如果要在位图上绘制某些内容并保存，请从位图创建图形：

using(Bitmap bitmap = new Bitmap(Width, Height))
using (Graphics graphics = Graphics.FromImage(bitmap))
{
    Rectangle rect = new Rectangle(0, 0, Width, Height);
    graphics.FillRectangle(new SolidBrush(BackColor), rect);
    graphics.DrawString("Hello, World", Font, new SolidBrush(ForeColor), rect);
    bitmap.Save(@"D:\hello_world.bmp");
} 

如果要在控件上绘制并将其图像保存到文件，请使用方法

顺便说一句，位图应该有

.bmp

扩展名，它不是JPEG图像