C#调用开源图像识别类库tessnet2

首先下载tessnet2_32.dll及相关语言包，将dll加入引用

       private tessnet2.Tesseract ocr = new tessnet2.Tesseract();//声明一个OCR类


            //程序开始的时候，初始化OCR
       ocr.SetVariable("tessedit_char_whitelist", "0123456789."); //设置识别变量，当前只能识别数字。
        ocr.Init(@"D:\tessdata", "eng", false); //应用当前语言包。注，Tessnet2是支持多国语的。语言包下载链接：http://code.google.com/p/tesseract-ocr/downloads/list


//下边这个函数是将网络上的图片识别成字符串，传入图片的超链接，输出字符串

        public string Bmp2Str(string bmpurl)

        {
            //http://www.newwhy.com/2010/0910/13708.html
            string s = "0";
            WebClient wc = new WebClient();
            try
            {
                byte[] oimg = wc.DownloadData(bmpurl);//将要识别的图像下载下来
                MemoryStream ms = new MemoryStream(oimg);
                Bitmap image = new Bitmap(ms);


//为了提高识别率，所以对图片进行简单的处理
                image = BlackAndWhite(image, 0.8);//黑白处理，这个函数看下边
                image = new Bitmap(image, image.Width * 3, image.Height * 3);//放大三倍

                Monitor.Enter(this);//因为是多线程，所以用到了Monitor。
                System.Collections.Generic.List<tessnet2.Word> result = ocr.DoOCR(image, Rectangle.Empty);//执行识别操作
                foreach (tessnet2.Word word in result) //遍历识别结果。
                    s = s + word.Text;
                Monitor.Exit(this);
                if (s.Length > 2)
                    s = s.Substring(2, s.Length - 2);

            }
            catch
            {
                s = "0";
            }
            finally
            {
                wc.Dispose();
            }
            return s;


            //Console.WriteLine("{0} : {1}", word.Confidence, word.Text);
        }





//黑白处理的函数，网上查的。

        public static Bitmap BlackAndWhite(Bitmap bitmap, Double hsb)
        {
            if (bitmap == null)
            {
                return null;
            }


            int width = bitmap.Width;
            int height = bitmap.Height;
            try
            {
                Bitmap bmpReturn = new Bitmap(width, height, PixelFormat.Format1bppIndexed);
                BitmapData srcBits = bitmap.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb);
                BitmapData targetBits = bmpReturn.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadWrite, PixelFormat.Format1bppIndexed);


                unsafe
                {
                    byte* pSrcBits = (byte*)srcBits.Scan0.ToPointer();
                    for (int h = 0; h < height; h++)
                    {
                        byte[] scan = new byte[(width + 7) / 8];
                        for (int w = 0; w < width; w++)
                        {
                            int r, g, b;
                            r = pSrcBits[2];
                            g = pSrcBits[1];
                            b = pSrcBits[0];


                            if (GetBrightness(r, g, b) >= hsb) scan[w / 8] |= (byte)(0x80 >> (w % 8));
                            pSrcBits += 3;
                        }
                        Marshal.Copy(scan, 0, (IntPtr)((int)targetBits.Scan0 + targetBits.Stride * h), scan.Length);
                        pSrcBits += srcBits.Stride - width * 3;
                    }
                    bmpReturn.UnlockBits(targetBits);
                    bitmap.UnlockBits(srcBits);
                    return bmpReturn;
                }
            }
            catch
            {
                return null;
            }


        }