最近研究C#相关的OCR技术，图像识别一般C和C++这种底层语言做的比较多，C#主要是依托一些封装好的组件进行调用，这里介绍三种身份证识别的方法。

一：调用大公司API接口，百度、云脉，文通科技都有相关的API介绍。
二：调用图像处理类库，EmguCV是OpenCV的一个跨平台的.Net封装，该封装也可以被编译到Mono平台和允许在Windows、Mac OS、Android、iPhone、iPad等多个平台上运行
三：调用Office2007 组件

一、证件识别API接口

以聚合数据中的API接口为例，因为官方API没有提供C#的调用方式，网址如下：证件识别接口

/// 

/// 上传图片

/// 

/// 

public static string CardUpload()

{

    try

    {

        string appkey = "网站自己申请的key"; //配置您申请的appkey         

        HttpPostedFile file = HttpContext.Current.Request.Files[0];

        string url = "http://api2.juheapi.com/cardrecon/upload";

        var parameters = new Dictionary<string, string>();

        parameters.Add("key", appkey);

        parameters.Add("cardType", "2");

        string result = HttpPostData(url, 60000, "pic", file.InputStream, parameters);

        JObject info = JObject.Parse(JObject.Parse(result)["result"].ToString());

        var cardInfo = new

        {

            name = info["姓名"],

            card = info["公民身份号码"]

        };

        return cardInfo.ToJson();

    }

    catch (Exception ex)

    {

        return ex.ToString();

    }

}

/// 

/// Post调用API

/// 

/// api地址

/// 访问超时时间

/// 文件参数名

/// 文件流

/// 参数列表

/// 结果集

private static string HttpPostData(string url, int timeOut, string fileKeyName,

                           Stream file, Dictionary<string, string> stringDict)

{

    string responseContent;

    var memStream = new MemoryStream();

    var webRequest = (HttpWebRequest)WebRequest.Create(url);

    // 边界符

    var boundary = "---------------" + DateTime.Now.Ticks.ToString("x");

    // 边界符

    var beginBoundary = Encoding.ASCII.GetBytes("--" + boundary + "\r\n");

    // 最后的结束符

    var endBoundary = Encoding.ASCII.GetBytes("--" + boundary + "--\r\n");

    // 设置属性

    webRequest.Method = "POST";

    webRequest.Timeout = timeOut;

    webRequest.ContentType = "multipart/form-data; boundary=" + boundary;

    //写入开始边界符

    memStream.Write(beginBoundary, 0, beginBoundary.Length);

    // 写入文件

    const string filePartHeader =

        "Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"\r\n" +

         "Content-Type: application/octet-stream\r\n\r\n";

    var header = string.Format(filePartHeader, fileKeyName, "card.jpg");

    var headerbytes = Encoding.UTF8.GetBytes(header);

    memStream.Write(headerbytes, 0, headerbytes.Length);

    file.CopyTo(memStream);

    // 写入字符串的Key

    var stringKeyHeader = "\r\n--" + boundary +

                           "\r\nContent-Disposition: form-data; name=\"{0}\"" +

                           "\r\n\r\n{1}\r\n";

    foreach (byte[] formitembytes in from string key in stringDict.Keys

                                     select string.Format(stringKeyHeader, key, stringDict[key])

                                         into formitem

                                         select Encoding.UTF8.GetBytes(formitem))

    {

        memStream.Write(formitembytes, 0, formitembytes.Length);

    }

    // 写入最后的结束边界符

    memStream.Write(endBoundary, 0, endBoundary.Length);

    webRequest.ContentLength = memStream.Length;

    // 构造完毕，执行POST方法

    var requestStream = webRequest.GetRequestStream();

    memStream.Position = 0;

    var tempBuffer = new byte[memStream.Length];

    memStream.Read(tempBuffer, 0, tempBuffer.Length);

    memStream.Close();

    requestStream.Write(tempBuffer, 0, tempBuffer.Length);

    requestStream.Close();

    var httpWebResponse = (HttpWebResponse)webRequest.GetResponse();

    using (var httpStreamReader = new StreamReader(httpWebResponse.GetResponseStream(),

                                                    Encoding.GetEncoding("utf-8")))

    {

        responseContent = httpStreamReader.ReadToEnd();

    }

    httpWebResponse.Close();

    webRequest.Abort();

    return responseContent;

}

二、EmguCV类库调用

环境搭建

下载地址：EmguCV官网

在File类别下下载这个EXE，进行安装，安装后在目录下能找相应组件，还有些应用的案例。

C#进行识别，需进行图片二值化处理和OCR调用相关DLL可在我整理的地址下载：360云盘 提取码：89f4
dll文件夹中的dll引用到C#项目中，x64，x86，tessdata对应OCR识别的类库和语言库，我tessdata中已添加中文语言包，将这三个文件夹放入程序执行文件夹中。

Demo

自己做的小Demo如图：身份证图片是百度上下载的

相关代码如下：

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

using Emgu.CV;

using Emgu.CV.OCR;

using Emgu.CV.Structure;

using System.IO;

namespace ImageManage

{

    public partial class Form1 : Form

    {

        Image imageThreshold;

        public Form1()

        {

            InitializeComponent();

        }

        private void btn_convert_Click(object sender, EventArgs e)

        {

            //第一个参数是语言包文件夹的地址，不写默认在执行文件夹下

            Tesseract _ocr = new Tesseract("", "chi_sim", OcrEngineMode.TesseractOnly);

            _ocr.Recognize(imageThreshold);

            String text = _ocr.GetText();

            this.textBox1.Text = text;

        }

        private void pictureBox1_Click(object sender, EventArgs e)

        {

            OpenFileDialog of = new OpenFileDialog();

            of.Title = "请选择图片";

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

            {

                string file = of.FileName;

                Image img = Image.FromFile(file);

                pictureBox1.Image = img;            

            }

            Bitmap bitmap = (Bitmap)this.pictureBox1.Image;

            Image imageSource = new Imagebyte>(bitmap);

            Image imageGrayscale = imageSource.Convert();

            imageGrayscale = randon(imageGrayscale);

            imageThreshold = imageGrayscale.ThresholdBinary(new Gray(100), new Gray(255));

            this.pictureBox2.Image = imageThreshold.ToBitmap();

        }

        /// 

        /// 旋转校正

        /// 

        /// 

        /// 

        private Image randon(Image imageInput)//图像投影旋转法倾斜校正子函数定义

        {

            int nwidth = imageInput.Width;

            int nheight = imageInput.Height;

            int sum;

            int SumOfCha;

            int SumOfChatemp = 0;

            int[] sumhang = new int[nheight];

            Image resultImage = imageInput;

            Image ImrotaImage;

            //20度范围内的调整

            for (int ang = -20; ang < 20; ang = ang + 1)

            {

                ImrotaImage = imageInput.Rotate(ang, new Gray(1));

                for (int i = 0; i < nheight; i++)

                {

                    sum = 0;

                    for (int j = 0; j < nwidth; j++)

                    {

                        sum += ImrotaImage.Data[i, j, 0];

                    }

                    sumhang[i] = sum;

                }

                SumOfCha = 0;

                for (int k = 0; k < nheight - 1; k++)

                {

                    SumOfCha = SumOfCha + (Math.Abs(sumhang[k] - sumhang[k + 1]));

                }

                if (SumOfCha > SumOfChatemp)

                {

                    resultImage = ImrotaImage;

                    SumOfChatemp = SumOfCha;

                }

            }

            return resultImage;

        }

    }

}

三、Office 2007组件

该组件免费而且识别度比较高。

环境搭建

Office 2007组件MODI，需要安装Ofiice2007，且由于兼容性需要安装补丁，SP1或者SP2都行，补丁下载地址如下：
SP1下载地址 SP2下载地址

安装后控制面板-->卸载或更新程序-->选择Office2007-->选择更改-->选择添加或修复功能-->弹出下面界面，运行相应组件。

将Office工具-->Microsoft Office Document Imaging 下的工具运行

在C#项目中引用Com组件即可：

如果Office组件应用不是在本地程序而需要部署在IIS上，还需将应用程序的应用池的权限设置为如下图所示：程序应用池-->高级设置-->标识

Demo