Github上有許多已經訓練好的分類器，可以直接拿來試用。

void Start()
{
    //訓練集路徑
    haarcascade_frontalface_default_xml_filepath = Application.dataPath + "/Cascades/haarcascade_frontalface_default.xml";
    haarcascade_eye_xml_filepath = Application.dataPath + "/Cascades/haarcascade_eye.xml";

    //讀取原圖
    srcMat = Imgcodecs.imread
 
(Application.dataPath + "/Textures/face.jpg", 1);
    Imgproc.cvtColor(srcMat, srcMat, Imgproc.COLOR_BGR2RGB);
    //轉為灰度影象
    grayMat = new Mat();
    Imgproc.cvtColor(srcMat, grayMat, Imgproc.COLOR_RGB2GRAY);

    //檢測影象中的所有臉
    MatOfRect faces = new MatOfRect();
    CascadeClassifier cascade = new CascadeClassifier(haarcascade_frontalface_default_xml_filepath);
 

    cascade.detectMultiScale(grayMat, faces, 1.1d, 2, 2, new Size(20, 20), new Size());
    //Debug.Log(faces); //檢測到多少個臉 [ elemSize*1*CV_32SC4, isCont=True, isSubmat=False, nativeObj=0x1128611568, dataAddr=0x0 ]
    OpenCVForUnity.Rect[] rects = faces.toArray();
    for (int i = 0; i < rects.Length; i++)
 

    {
        //Debug.Log("detect faces " + rects[i]);
        Imgproc.rectangle(srcMat, new Point(rects[i].x, rects[i].y), new Point(rects[i].x + rects[i].width, rects[i].y + rects[i].height), new Scalar(0, 255, 0, 255), 2); //綠

        //眼長在臉上
        Mat roi_gray_img = new Mat(grayMat, new OpenCVForUnity.Rect(0, 0, rects[i].x + rects[i].width, rects[i].y + rects[i].height));
        Mat roi_img = new Mat(srcMat, new OpenCVForUnity.Rect(0, 0, rects[i].x + rects[i].width, rects[i].y + rects[i].height));
        MatOfRect eyes = new MatOfRect();
        CascadeClassifier eyecascade = new CascadeClassifier(haarcascade_eye_xml_filepath);
        eyecascade.detectMultiScale(roi_gray_img, eyes, 1.3d, 5, 2, new Size(20, 20), new Size());
        //Debug.Log(eyes.elemSize());
        if (eyes.elemSize() > 0)
        {
            OpenCVForUnity.Rect[] eye_rects = eyes.toArray();
            for (int t = 0; t < eye_rects.Length; t++)
            {
                //Debug.Log("detect eyes " + rects[t]);
                //Imgproc.rectangle(roi_img, new Point(eye_rects[t].x, eye_rects[t].y), new Point(eye_rects[t].x + eye_rects[t].width, eye_rects[t].y + eye_rects[t].height), new Scalar(255, 255, 0, 255), 2); //黃
                Point center = new Point((eye_rects[t].x + eye_rects[t].x + eye_rects[t].width) / 2, (eye_rects[t].y + eye_rects[t].y + eye_rects[t].height) / 2);
                Imgproc.circle(roi_img, center, eye_rects[t].width / 2, new Scalar(255, 255, 0, 255), 2);
            }
        }
    }

    Texture2D t2d = new Texture2D(srcMat.width(), srcMat.height());
    Utils.matToTexture2D(srcMat, t2d);
    Sprite sp = Sprite.Create(t2d, new UnityEngine.Rect(0,0, t2d.width, t2d.height), Vector2.zero);
    m_srcImage.sprite = sp;
    m_srcImage.preserveAspect = true;
}

最終效果