C#实现在现有图片的指定位置添加文字

添加引用：
using System.Drawing;
using System.Drawing.Imaging;

public Bitmap CreateBMP(Image image)
        {
            //声明位图
            Bitmap bitmap = new Bitmap(image, image.Width, image.Height);
            return bitmap;
        }


    public Graphics CreateGraphics(Bitmap bt)
    {
        Graphics g1 = Graphics.FromImage(bt);
        //设置图像质量
        g1.CompositingQuality = CompositingQuality.HighQuality;
        g1.SmoothingMode = SmoothingMode.HighQuality;
        g1.InterpolationMode = InterpolationMode.HighQualityBicubic;
        return g1;
    }

    /// <summary>
    /// 在现有画布上添加文字
    /// </summary>
    /// <param name="g">画布对象</param>
    /// <param name="txt">需要添加的文字</param>
    /// <param name="fontName">字体名称</param>
    /// <param name="fontSize">字体大小</param>
    /// <param name="fontStyle">字体风格，是否加粗等</param>
    /// <param name="x">绘画位置X</param>
    /// <param name="y">绘画位置Y</param>
    /// <param name="red">文字颜色R</param>
    /// <param name="green">文字颜色G</param>
    /// <param name="blue">文字颜色B</param>
    public void drawText(Graphics g,string txt,string fontName,int fontSize,FontStyle fontStyle,float x,float y,int red,int green,int blue)
    {
        //文字绘制
        Font font = new Font(fontName, fontSize, fontStyle, GraphicsUnit.Pixel);
        Brush brush = new SolidBrush(Color.FromArgb(red, green, blue));
        g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAliasGridFit;
        g.DrawString(txt, font, brush, x, y, StringFormat.GenericDefault);
        //string path = "D:\\test.png";
        //bitmap.Save(path, System.Drawing.Imaging.ImageFormat.Gif);
    }