【亲测可行，图片宽度高度自适应】c# Graphics MeasureString精确测量字体宽度

 public static Bitmap GetImage(string number, float fontSize, int color_red = 40, int color_green = 124, int color_blue = 254)
        {
            int count = number.Length;

            //需要配置的字段
            //Font f = new Font("Microsoft Sans Serif", fontSize);//, System.Drawing.FontStyle.Bold);//设置字体样式，大小
            Font f = new Font("思源宋体", fontSize);//, System.Drawing.FontStyle.Bold);//设置字体样式，大小
            #region 测量字体宽度
            Bitmap image_size = new Bitmap(20 * count, f.Height);//初始化大小
            Graphics size_g = Graphics.FromImage(image_size);

            SizeF sizeF = size_g.MeasureString(number, f);
            #endregion

            Bitmap image = new Bitmap((int)sizeF.Width, (int)sizeF.Height);//初始化大小

            Random random = new Random();
            try
            {
                Graphics g = Graphics.FromImage(image);
                g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;//设置图片质量
                g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;//.Drawing.Text.TextRenderingHint.SingleBitPerPixel;
                g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
                g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;

                Brush b = new SolidBrush(Color.FromArgb(color_red, color_green, color_blue));
                RectangleF rectangleF = new RectangleF(0, 0, sizeF.Width, sizeF.Height);
                //设置位置
                g.DrawString(number, f, b, rectangleF);

                return image;
            }
            finally { }
        }