C#使用Emgu CV来进行图片人脸检测

项目需求：某市级组织考试，在考试前需审核考生采集表中的考生照片是否合格，由于要审核的考生信息采集表有很多，原先进行的是手动人工审核，比较费时费力，审核的要求也很简单，并不判断考生是否是图片本人（身份验证有另外一套程序来进行），只是看考生采集表中考生头像是否是人脸（是否存在辨识不清楚，不是人脸）。因此提出需求，看是否能用程序来检测考生信息采集表中的照片，只需找出来疑似不是人脸的考生所在文档位置（pdf文档）即可，存疑的考生再由人工进行审核。

PDF文档中有很多页，每一页都是如图中的结构。

经过百度摸索，采用了C#+WPF+Spire.PDF+Emgu CV+MvvmLight来进行人脸判断的技术选型。

Emgu CV(https://sourceforge.net/projects/emgucv/files/emgucv/)是.NET平台下对OpenCV图像处理库的封装，也就是.NET版的
OpenCV的全称是：Open Source Computer Vision Library。OpenCV是一个基于（开源）发行的跨平台计算机视觉库，可以运行在Linux、Windows和Mac OS操作系统上。Emgu CV官方带的有训练过的人脸识别模板，可以直接使用。

Spire.PDF可以来读取PDF文档，同时可以读取到PDF文档中的图片。

MvvmLight是WPF可以使用的一种MVVM模式的实现框架。

项目技术选型确定以后，下面就是代码的编写。

项目引用Emgu CV、Spire.PDF、MvvmLight

从官网下载Emgu CV后，我们把它项目中的haarcascade_eye.xml、haarcascade_frontalface_alt.xml两个训练过的人脸识别模板放到bin/debug下，供Emgu CV使用时调用。

引用MvvmLight后，会自动在项目中创建ViewModel目录，我们在此目录中新建一个Pdf2FaceInfoModel.cs类，用来做为检测结果的通知类。

using System.ComponentModel;
  
namespace Pdf2Face.ViewModel
{
    public class Pdf2FaceInfoModel : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
  
        private string pdfName { get; set; }
        /// <summary>
        /// Pdf文件名
        /// </summary>
        public string PdfName
        {
            get => pdfName;
            set
            {
                pdfName = value;
                PropertyChanged?.Invoke(this,new PropertyChangedEventArgs("PdfName"));
            }
        }
  
        private int pdfImgCount { get; set; } = 0;
        /// <summary>
        /// Pdf中图片数量
        /// </summary>
        public int PdfImgCount
        {
            get => pdfImgCount;
            set
            {
                pdfImgCount = value;
                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("PdfImgCount"));
            }
        }
  
        private int pdfFaceCount { get; set; } = 0;
        /// <summary>
        /// Pdf中人脸数量
        /// </summary>
        public int PdfFaceCount
        {
            get => pdfFaceCount;
            set
            {
                pdfFaceCount = value;
                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("PdfFaceCount"));
            }
        }
  
        private string pdfFaceSuccess { get; set; } ="否";
        /// <summary>
        /// 数量相对是否存疑 0 正常 1存疑
        /// </summary>
        public string PdfFaceSuccess
        {
            get => pdfFaceSuccess;
            set
            {
                pdfFaceSuccess = value;
                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("PdfFaceSuccess"));
            }
        }
    }
}

主程序只有一个界面，界面两个按钮，一个用来选择要检测pdf所在文件夹，一个用来开始检测。

主程序代码：

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;
using Emgu.CV;
using Emgu.CV.Structure;
using Microsoft.WindowsAPICodePack.Dialogs;
using Pdf2Face.ViewModel;
using Spire.Pdf;
  
namespace Pdf2Face
{
    /// <summary>
    /// 人脸检测功能的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        private string _pdfDirPath;
        private readonly string _pdfFaceSaveDir;
        private readonly ObservableCollection<Pdf2FaceInfoModel> facelist = new ObservableCollection<Pdf2FaceInfoModel>();
  
        public MainWindow()
        {
            InitializeComponent();
            Thread.Sleep(10000);
            dataGrid.ItemsSource = facelist;
            _pdfFaceSaveDir = $"{AppDomain.CurrentDomain.BaseDirectory}face";
            if (!Directory.Exists(_pdfFaceSaveDir))
            {
                Directory.CreateDirectory(_pdfFaceSaveDir);
            }
        }
        /// <summary>
        /// 选择Pdf所在目录
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void BtnChooseDir_OnClick(object sender, RoutedEventArgs e)
        {
            using (var folderBrowser = new CommonOpenFileDialog())
            {
                folderBrowser.IsFolderPicker = true;
                folderBrowser.Multiselect = false;
                folderBrowser.Title = "选择考生照片所在文件夹";
                if (folderBrowser.ShowDialog(GetWindow(this)) != CommonFileDialogResult.Ok) return;
                _pdfDirPath = folderBrowser.FileName;
                txtBlockPath.Text = _pdfDirPath;
            }
        }
        /// <summary>
        /// 人脸识别检测
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void BtnCheck_OnClick(object sender, RoutedEventArgs e)
        {
            if (string.IsNullOrEmpty(_pdfDirPath) || !Directory.Exists(_pdfDirPath))
            {
                MessageBox.Show("目录无法访问。", "错误", MessageBoxButton.OK, MessageBoxImage.Error);
                return;
            }
  
            var pdfs = FileSearch(_pdfDirPath, "*.pdf", SearchOption.AllDirectories,
                x => x.Length > 6);
            if (pdfs.Length == 0)
            {
                MessageBox.Show("指定的目录中没有发现PDF文件。", "错误", MessageBoxButton.OK, MessageBoxImage.Information);
                return;
            }
  
            txtBlockInfo.Text = $"Pdf文件数量{pdfs.Length}";
            var doc = new PdfDocument();
  
            Dispatcher?.InvokeAsync(async () =>
            {
                await Task.Run(() =>
                {
                    foreach (var pdf in pdfs)
                    {
                        doc.LoadFromFile(pdf);
                        var pagenum = 1;
  
                        foreach (PdfPageBase page in doc.Pages)
                        {
                            var newPdfFaceSaveDir = $"{_pdfFaceSaveDir}\{pdf.Substring(pdf.LastIndexOf('\') + 1)}";
                            if (page.ExtractImages() != null)
                            {
                                if (!Directory.Exists(newPdfFaceSaveDir))
                                {
                                    Directory.CreateDirectory(newPdfFaceSaveDir);
                                }
                                var images = new List<Image>();
                                var model = new Pdf2FaceInfoModel
                                {
                                    PdfName = $"{pdf.Substring(pdf.LastIndexOf('\') + 1)}_第{pagenum}页"
                                };
                                Dispatcher?.Invoke(() =>
                                {
                                    facelist.Add(model);
  
                                });
                                var c = 0;
                                foreach (var image in page.ExtractImages())
                                {
                                    images.Add(image);
                                    var filename = $"{newPdfFaceSaveDir}\{pagenum}_{c}.png";
                                    image.Save(filename, ImageFormat.Png);
  
                                    #region 人脸判断
                                    //检测是否是人脸
                                    //如果支持用显卡,则用显卡运算
                                    CvInvoke.UseOpenCL = CvInvoke.HaveOpenCLCompatibleGpuDevice;
                                    //构建级联分类器,利用已经训练好的数据,识别人脸
                                    var face = new CascadeClassifier("haarcascade_frontalface_alt.xml");
                                    var eyes = new CascadeClassifier("haarcascade_eye.xml");
                                    //加载要识别的图片
                                    var img = new Image<Bgr, byte>(filename);
                                    var img2 = new Image<Gray, byte>(img.ToBitmap());
  
                                    //把图片从彩色转灰度
                                    CvInvoke.CvtColor(img, img2, Emgu.CV.CvEnum.ColorConversion.Bgr2Gray);
                                    //亮度增强
                                    CvInvoke.EqualizeHist(img2, img2);
                                    //返回的是人脸所在的位置和大小
                                    var facesDetected = face.DetectMultiScale(img2, 1.1, 10, new System.Drawing.Size(50, 50));                                   
  
                                    if (facesDetected.Length > 0)
                                    {
                                        model.PdfFaceCount += facesDetected.Length;
                                        model.PdfFaceSuccess = facesDetected.Length > 1 ? "是" : "否";
                                        //删除图片，留下的都是无法正确识别的
                                        try
                                        {
                                            File.Delete(filename);
                                        }
                                        catch (Exception exception)
                                        {
                                            //
                                        }
                                    }
  
                                    img.Dispose();
                                    img2.Dispose();
                                    face.Dispose();
                                    #endregion
  
                                    c += 1;
                                }
                                model.PdfImgCount = images.Count;
                            }
                            pagenum += 1;
                        }
                        doc.Close();
                    }
  
                });
            });
        }
  
        private string[] FileSearch(string directoryPath, string searchFilter, SearchOption option, Func<string, bool> func)
        {
            if (!Directory.Exists(directoryPath)) return null;
            var s = Directory.GetFiles(directoryPath, searchFilter, option).Where(func).ToArray();
            return s;
        }
  
        private void MainWindow_OnClosing(object sender, CancelEventArgs e)
        {
            Application.Current.Shutdown(0);
        }
    }
}

程序运行效果：