OpenCV in Python

Question

Code runs but instead of posting my name during the detector.py it says unknown. Anyone have any solutions?

import cv2
import numpy as np


recognizer = cv2.face.LBPHFaceRecognizer_create()
recognizer.read('trainer/trainer.yml')
cascadePath = "haarcascade_frontalface_default.xml"
faceCascade = cv2.CascadeClassifier(cascadePath);
font = cv2.FONT_HERSHEY_SIMPLEX
cam = cv2.VideoCapture(0)


while True:
    ret, im =cam.read()
    gray = cv2.cvtColor(im,cv2.COLOR_BGR2GRAY)
    faces = faceCascade.detectMultiScale(gray, 1.2,5)


for(x,y,w,h) in faces:
   cv2.rectangle(im, (x-20,y-20), (x+w+20,y+h+20), (0,255,0), 4)
   Id = recognizer.predict(gray[y:y+h,x:x+w])
    if(Id == 1):
        Id = "Alec"
    elif(Id == 2):
         Id = "Chase"
    else:
        Id = "Unknown"
    cv2.rectangle(im, (x-22,y-90), (x+w+22, y-22), (0,255,0), -1)
    cv2.putText(im, str(Id), (x,y-40), font, 2, (255,255,255), 3)
if cv2.waitKey(10) & 0xFF == ord('q'):
    break


cam.release()
cv2.destroyAllWindows()

It is not showing any types of error. I have commented out the If(id==X) code just to see what it would print on the screen. The program printed (1, 30-40). So I'm guessing the 1 is my ID. I have the DataSet and trainer program if I need to provide it.

alkasm · Accepted Answer · 2017-12-05 02:16:24Z

1

recognizer.predict returns both the Id and confidence score.

    Id, conf = recognizer.predict(gray[y:y+h,x:x+w])
    if(conf<50):
        if(Id==1):
            Id="asciime"
        elif(Id==2):
            Id="Something"
    else:
        Id="Unknown"

OpenCV's Python API documentation is very poor. I often use the C++ reference. In this case the predict method is

void cv::face::FaceRecognizer::predict(InputArray src, int& label, double& confidence)  const

See https://docs.opencv.org/3.2.0/dd/d65/classcv_1_1face_1_1FaceRecognizer.html#ab0d593e53ebd9a0f350c989fcac7f251 .

edited Dec 5, 2017 at 2:16

alkasm

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answered Dec 1, 2017 at 6:54

Vu Gia Truong

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3 Comments

alkasm Over a year ago

Can you link to some documentation so the OP has a resource to understand the outputs of the predict() method?

Vu Gia Truong Over a year ago

I add link and some explaination in the answer

alkasm Over a year ago

Great! Nice answer.

Bart748 · Accepted Answer · 2017-12-04 14:01:56Z

Confidence is standard set to 50. However the Id has 2 values in it. the int(ID) and double(Conf). https://docs.opencv.org/3.0.0/dd/d65/classcv_1_1face_1_1FaceRecognizer.html#aede3fa2ec7a4ee35e67bc998df23883b getting the first value with Id[1] would work

for(x,y,w,h) in faces:
  cv2.rectangle(im, (x-20,y-20), (x+w+20,y+h+20), (0,255,0), 4)
  Id = recognizer.predict(gray[y:y+h,x:x+w])
    if(Id[1] == 1):
       Id = "Alec"
    elif(Id[1] == 2):
       Id = "Chase"
    else:
       Id = "Unknown"
  cv2.rectangle(im, (x-22,y-90), (x+w+22, y-22), (0,255,0), -1)
  cv2.putText(im, str(Id), (x,y-40), font, 2, (255,255,255), 3)
if cv2.waitKey(10) & 0xFF == ord('q'):
   break

or

for(x,y,w,h) in faces:
   cv2.rectangle(im, (x-20,y-20), (x+w+20,y+h+20), (0,255,0), 4)
   Id,conf = recognizer.predict(gray[y:y+h,x:x+w])
     if(Id == 1):
        Id = "Alec"
     elif(Id == 2):
        Id = "Chase"
     else:
        Id = "Unknown"
  cv2.rectangle(im, (x-22,y-90), (x+w+22, y-22), (0,255,0), -1)
  cv2.putText(im, str(Id), (x,y-40), font, 2, (255,255,255), 3)
if cv2.waitKey(10) & 0xFF == ord('q'):
    break

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