C# - 检测人脸和裁剪图像

Question

我正在用 C# 编写一个 HttpHandler，它提供调整大小的图像和 blah blah blah...没问题，我们有数百万个处理程序可供引用。

问题是我的用户使用“传统”尺寸拍摄的照片，例如 4:3 和 16:9。但是此处理程序需要提供照片 ID 大小(4 厘米 x 3 厘米)的图片，并且显然需要在用户面部周围裁剪。面部位置变化很大(并不总是在图片中心)。

那么，我可以使用什么样的算法来检测面部中心，然后围绕该点裁剪图像？

Answer 1

您可以在 EmguCV(OpenCV 的 DotNet 端口)中使用 HaarCascade 类 http://www.emgu.com/wiki/index.php/Face_detection

Notes in order to run this example:

• Create a Windows Form Application
• Add a PictureBox and a Timer (and Enable it) - Run it on a x86 system
• Be sure you have the OpenCV relevant dlls (included with the Emgu CV download) in the folder where you code executes.
• Adjust the path to find the Haarcascade xml (last line of the code)

using System;
using System.Windows.Forms;
using System.Drawing;
using Emgu.CV;
using Emgu.Util;
using Emgu.CV.Structure;
using Emgu.CV.CvEnum;
 
namespace opencvtut
{
    public partial class Form1 : Form
    {
                private Capture cap;
                private HaarCascade haar;
 
        public Form1()
        {
            InitializeComponent();
        }
 
        private void timer1_Tick(object sender, EventArgs e)
        {
                using (Image<Bgr, byte> nextFrame = cap.QueryFrame())
                {
                        if (nextFrame != null)
                        {
                                // there's only one channel (greyscale), hence the zero index
                                //var faces = nextFrame.DetectHaarCascade(haar)[0];
                                Image<Gray, byte> grayframe = nextFrame.Convert<Gray, byte>();
                                var faces =
                                        grayframe.DetectHaarCascade(
                                                haar, 1.4, 4,
                                                HAAR_DETECTION_TYPE.DO_CANNY_PRUNING,
                                                new Size(nextFrame.Width/8, nextFrame.Height/8)
                                                )[0];
 
                                foreach (var face in faces)
                                {
                                        nextFrame.Draw(face.rect, new Bgr(0,double.MaxValue,0), 3);
                                }
                                pictureBox1.Image = nextFrame.ToBitmap();
                        }
                }
        }
 
        private void Form1_Load(object sender, EventArgs e)
        {
            // passing 0 gets zeroth webcam
                        cap = new Capture(0);
            // adjust path to find your xml
                        haar = new HaarCascade(
                "..\\..\\..\\..\\lib\\haarcascade_frontalface_alt2.xml");
        }
    }
}