當麻許的超技八

/// <summary>

 /// 製作Captcha

 /// </summary>

 /// <param name="text">文字</param>

 /// <param name="fontName">字體名稱</param>

 /// <param name="backgroundImagePath">採樣的背景圖</param>

 /// <param name="width">結果的圖片寬度</param>

 /// <param name="height">結果的圖片高度</param>

 /// <param name="fontSize"> 字體大小</param>

 /// <param name="waterEffect">增加漣漪複雜度 </param>

 /// <returns></returns>

 public Bitmap GetCaptcha(string text, string fontName, string backgroundImagePath, int width, int height, int fontSize, short waterEffect = 10)

 {

     var backImage = new Bitmap(backgroundImagePath);

     //如果原圖過小 就以原圖大小為主

     if (backImage.Width < width || backImage.Height < height)

     {

         throw new Exception("結果尺寸不得小於採樣大小的圖片");

     }

     //隨機取一個位置 並且按造欲需求的大小裁切

     //請注意隨機採樣範圍 記得為 圖片寬度-欲取的寬度 高度也是 ，不然會發生裁切超過範圍

     backImage =

        backImage.Clone(

            new Rectangle(new Random().Next(0, backImage.Width - width),

                          new Random().Next(0, backImage.Height - height), width, height), backImage.PixelFormat);

     Graphics graphics = Graphics.FromImage(backImage);

     //合成的文字為黑色

     Brush br = new SolidBrush(Color.Black);

     //將字體畫上圖片

     //字體的大小 為 自訂

     graphics.DrawString(text, new Font(new FontFamily(fontName), fontSize), br, new PointF(0, 0));

     //增加複雜度

     backImage = AdjustRippleEffect(backImage, waterEffect);

     return backImage;

 }

 /// <summary>

 /// 水波紋效果

 /// </summary>

 /// <param name="src"></param>

 /// <param name="nWave">坡度</param>

 /// <returns></returns>

 public Bitmap AdjustRippleEffect(Bitmap src, short nWave)

 {

     int nWidth = src.Width;

     int nHeight = src.Height;

     // 透過公式進行水波紋的採樣

     FloatPoint[,] fp = new FloatPoint[nWidth, nHeight];

     Point[,] pt = new Point[nWidth, nHeight];

     Point mid = new Point();

     mid.X = nWidth / 2;

     mid.Y = nHeight / 2;

     double newX, newY;

     double xo, yo;

     //先取樣將水波紋座標跟RGB取出

     for (int x = 0; x < nWidth; ++x)

         for (int y = 0; y < nHeight; ++y)

         {

             xo = ((double)nWave * Math.Sin(2.0 * 3.1415 * (float)y / 128.0));

             yo = ((double)nWave * Math.Cos(2.0 * 3.1415 * (float)x / 128.0));

             newX = (x + xo);

             newY = (y + yo);

             if (newX > 0 && newX < nWidth)

             {

                 fp[x, y].X = newX;

                 pt[x, y].X = (int)newX;

             }

             else

             {

                 fp[x, y].X = 0.0;

                 pt[x, y].X = 0;

             }

             if (newY > 0 && newY < nHeight)

             {

                 fp[x, y].Y = newY;

                 pt[x, y].Y = (int)newY;

             }

             else

             {

                 fp[x, y].Y = 0.0;

                 pt[x, y].Y = 0;

             }

         }

     //進行合成

     Bitmap bSrc = (Bitmap)src.Clone();

     // 依照 Format24bppRgb 每三個表示一 Pixel 0: 藍 1: 綠 2: 紅

     BitmapData bitmapData = src.LockBits(new Rectangle(0, 0, src.Width, src.Height), ImageLockMode.ReadWrite,

                                    PixelFormat.Format24bppRgb);

     BitmapData bmSrc = bSrc.LockBits(new Rectangle(0, 0, bSrc.Width, bSrc.Height), ImageLockMode.ReadWrite,

                                      PixelFormat.Format24bppRgb);

     int scanline = bitmapData.Stride;

     IntPtr Scan0 = bitmapData.Scan0;

     IntPtr SrcScan0 = bmSrc.Scan0;

     unsafe

     {

         byte* p = (byte*)(void*)Scan0;

         byte* pSrc = (byte*)(void*)SrcScan0;

         int nOffset = bitmapData.Stride - src.Width * 3;

         int xOffset, yOffset;

         for (int y = 0; y < nHeight; ++y)

         {

             for (int x = 0; x < nWidth; ++x)

             {

                 xOffset = pt[x, y].X;

                 yOffset = pt[x, y].Y;

                 if (yOffset >= 0 && yOffset < nHeight && xOffset >= 0 && xOffset < nWidth)

                 {

                     p[0] = pSrc[(yOffset * scanline) + (xOffset * 3)];

                     p[1] = pSrc[(yOffset * scanline) + (xOffset * 3) + 1];

                     p[2] = pSrc[(yOffset * scanline) + (xOffset * 3) + 2];

                 }

                 p += 3;

             }

             p += nOffset;

         }

     }

     src.UnlockBits(bitmapData);

     bSrc.UnlockBits(bmSrc);

     return src;

 }

 private struct FloatPoint

 {

     public double X;

     public double Y;

 }

Helper helper=new Helper();

var result=helper.GetCaptcha("我是當麻", "微軟正黑體",Server.MapPath("bk.jpg"),120,40,20);

Helper helper=new Helper();

var result = helper.GetCaptcha("ABCDE", "Verdana", Server.MapPath("bk.jpg"), 100, 40, 20, 12);