C#版Tesseract库的使用技巧_C#

上一篇介绍了Tesseract库的使用（OCR库Tesseract初探），文末提到了Tesseract是用c/c++开发的，也有C#的开源版本，本篇介绍一下如何使用C#版的Tesseract。

C#版本源码下载地址：https://github.com/charlesw/tesseract

其实在vs中可以直接用NuGet工具进行下载：

打开nuget，搜索tesseract，点安装即可。

C#版Tesseract库的使用技巧

源码是vs2015编译的，需要安装vs2015以上版本。

打开项目后如：

C#版Tesseract库的使用技巧

我们再添加一个winform项目，画界面如：

C#版Tesseract库的使用技巧

实现点击“选择需要识别的图片”，打开一张图片，调用算法并显示结果。比较简单。源码如下：

				?

									using System;

									using System.Collections.Generic;

									using System.ComponentModel;

									using System.Data;

									using System.Drawing;

									using System.Linq;

									using System.Text;

									using System.Threading.Tasks;

									using System.Windows.Forms;

									using Tesseract;

									namespace TesseractDemo

									{

									    public partial class Form1 : Form

									    {

									        public Form1()

									        {

									            InitializeComponent();

									        }

									        //选图片并调用ocr识别方法

									        private void btnRec_Click(object sender, EventArgs e)

									        {

									            //openFileDialog1.Filter = "";

									            if (openFileDialog1.ShowDialog() == DialogResult.OK)

									            {

									                var imgPath = openFileDialog1.FileName;

									                pictureBox1.Image=Image.FromFile(imgPath);

									                string strResult = ImageToText(imgPath);

									                if (string.IsNullOrEmpty(strResult))

									                {

									                    txtResult.Text = "无法识别";

									                }

									                else

									                {

									                    txtResult.Text = strResult;

									                }

									            }

									        }

									        //调用tesseract实现OCR识别

									        public string ImageToText(string imgPath)

									        {

									            using (var engine = new TesseractEngine("tessdata", "eng", EngineMode.Default))

									            {

									                using (var img = Pix.LoadFromFile(imgPath))

									                {

									                    using (var page = engine.Process(img))

									                    {

									                        return page.GetText();

									                    }

									                }

									            }

									        }

									    }

									}

有一点要注意的是，tesseract的识别语言包要自己下载后包含到项目里面，并设置为始终复制，或者直接把这个文件包放到运行程序目录（bin\debug)下：

C#版Tesseract库的使用技巧

eng是英文字符的意思，要识别其他语言字符，需要自己下载：

Tesseract hasunicode (UTF-8) support, and canrecognize more than 100 languages"out of the box".

这个库支持100种语言的识别

字库下载地址为：https://github.com/tesseract-ocr/tessdata

用OpencvSharp先降噪再调OCR识别：

				?

									//用opencv进行降噪处理再ocr识别

									        private void button3_Click(object sender, EventArgs e)

									        {

									            //从网上读取一张图片

									            string imgUrl = "https://service.cheshi.com/user/validate/validatev3.php";

									            MemoryStream ms = ReadImgFromWeb(imgUrl);

									            Image img = Image.FromStream(ms);

									            pictureBox1.Image = img;

									            //降噪

									            Mat simg = Mat.FromStream(ms, ImreadModes.Grayscale);

									            Cv2.ImShow("Input Image", simg);

									            //阈值操作 阈值参数可以用一些可视化工具来调试得到

									            Mat ThresholdImg = simg.Threshold(29, 255, ThresholdTypes.Binary);

									            Cv2.ImShow("Threshold", ThresholdImg);

									            Cv2.ImWrite("d:\\img.png", ThresholdImg);

									            textBox1.Text= ImageToText("d:\\img.png");

									        }

									        /// <summary>

									        /// 从网上读取一张图片

									        /// </summary>

									        /// <param name="Url"></param>

									        public MemoryStream ReadImgFromWeb(string Url)

									        {

									            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);

									            request.Credentials = CredentialCache.DefaultCredentials; // 添加授权证书

									            request.UserAgent = "Microsoft Internet Explorer";

									            WebResponse response = request.GetResponse();

									            Stream s = response.GetResponseStream();

									            byte[] data = new byte[1024];

									            int length = 0;

									            MemoryStream ms = new MemoryStream();

									            while ((length = s.Read(data, 0, data.Length)) > 0)

									            {

									                ms.Write(data, 0, length);

									            }

									            ms.Seek(0, SeekOrigin.Begin);

									            //pictureBox1.Image = Image.FromStream(ms);

									            return ms;

									        }