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

/// <summary>
/// 上传图片
/// </summary>
/// <returns></returns>
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();
    }
}
/// <summary>
/// Post调用API
/// </summary>
/// <param name="url">api地址</param>
/// <param name="timeOut">访问超时时间</param>
/// <param name="fileKeyName">文件参数名</param>
/// <param name="file">文件流</param>
/// <param name="stringDict">参数列表</param>
/// <returns>结果集</returns>
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<Gray, Byte> 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<Bgr, Byte> imageSource = new Image<Bgr, byte>(bitmap);
            Image<Gray, Byte> imageGrayscale = imageSource.Convert<Gray, Byte>();
            imageGrayscale = randon(imageGrayscale);
            imageThreshold = imageGrayscale.ThresholdBinary(new Gray(100), new Gray(255));
            this.pictureBox2.Image = imageThreshold.ToBitmap();
        }

        /// <summary>
        /// 旋转校正
        /// </summary>
        /// <param name="imageInput"></param>
        /// <returns></returns>
        private Image<Gray, Byte> randon(Image<Gray, Byte> 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<Gray, Byte> resultImage = imageInput;
            Image<Gray, Byte> 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

StringBuilder sb = new StringBuilder();
MODI.Document doc = new MODI.Document();
doc.Create(fullFileName);
MODI.Image image;
MODI.Layout layout;
doc.OCR(MODI.MiLANGUAGES.miLANG_CHINESE_SIMPLIFIED, true, true);  // 识别文字类型
for (int i = 0; i < doc.Images.Count; i++)
{
    image = (MODI.Image)doc.Images[i];
    layout = image.Layout;
    sb.Append(layout.Text);
}

以上即一些C#进行身份证识别的方法，可根据自己项目的不同需求进行选用。