How to Eliminate the Jagged Edge Effect of Captcha Image in C#

Introduction　

　　　　　 A mobile number to image conversion requirement was implemented based on the generated image. The content is quite simple, directly generating a PNG image with the mobile number. It is transparent for background purposes so that it can be called from other places. Whether there are anti-aliasing effects mainly depends on one line of code: g.TextRenderingHint = TextRenderingHint.AntiAlias;　

生成图片　　

1、有锯齿　

2、无锯齿

生成方法

string color = "#ff"6633";" 
    System.Drawing.Bitmap image = new System.Drawing.Bitmap(170, 35);
    Graphics g = Graphics.FromImage(image);
    try
    {
      g.TextRenderingHint= TextRenderingHint.AntiAlias; //Eliminate jaggies
      //Generate a random number generator
      Random random = new Random();
     //Clear the background color of the picture
      //g.Clear(Color.Transparent);
      //Draw the background noise lines of the picture
      /*for (int i = 0; i < 2; i++)
      {
        int x1 = random.Next(image.Width);
        int x2 = random.Next(image.Width);
        int y1 = random.Next(image.Height);
        int y2 = random.Next(image.Height);
        g.DrawLine(new Pen(Color.Black), x1, y1, x2, y2);
      }
      */
      System.Drawing.ColorConverter colConvert = new System.Drawing.ColorConverter();
      Color fontColor =(System.Drawing.Color)colConvert.ConvertFromString(color);
      Font font = new System.Drawing.Font("Arial", 18, System.Drawing.FontStyle.Bold);
      LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), fontColor, fontColor,LinearGradientMode.Horizontal);
      g.DrawString(phone, font, brush, 2, 2);
      //Draw the foreground noise points of the picture
       //for (int i = 0; i < 50; i++)
      //{
      //  int x = random.Next(image.Width);
      //  int y = random.Next(image.Height);
      //  image.SetPixel(x, y, Color.FromArgb(random.Next()));
      //}
      //Draw the border line of the picture
      //g.DrawRectangle(new Pen(Color.White), 0, 0, image.Width) - 1, image.Height - 1);
      System.IO.MemoryStream ms = new System.IO.MemoryStream();
      Color backColor = image.GetPixel(1, 1);
      image.MakeTransparent(backColor);
      image.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
      context.Response.ClearContent();
      context.Response.ContentType = "image/x-png";
      context.Response.BinaryWrite(ms.ToArray());
    }
    finally
    {
      g.Dispose();
      image.Dispose();
    }

References　

http://www.blue1000.com/bkhtml/c17/2013-03/71115.htm

That's all for this article. Hope it will be helpful to everyone's learning and also hope everyone will support the Yelling Tutorial more.

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