Authored by 2014Vee
Contact me via liuping@50yc.com

博主最近在做和人脸识别相关的项目：

在网上查找代码测试的过程中，发现网上大部分Python代码(如下)都会在运行后报错如下：

#!/usr/bin/python

#coding=utf-8

''' face detect

https://github.com/seathiefwang/FaceRecognition-tensorflow

http://tumumu.cn/2017/05/02/deep-learning-face/

'''

# pylint: disable=invalid-name

import os

import random

import numpy as np

import cv2



def createdir(*args):

    ''' create dir'''

    for item in args:

        if not os.path.exists(item):

            os.makedirs(item)



IMGSIZE = 64





def getpaddingSize(shape):

    ''' get size to make image to be a square rect '''

    h, w = shape

    longest = max(h, w)

    result = (np.array([longest]*4, int) - np.array([h, h, w, w], int)) // 2

    return result.tolist()



def dealwithimage(img, h=64, w=64):

    ''' dealwithimage '''

    #img = cv2.imread(imgpath)

    top, bottom, left, right = getpaddingSize(img.shape[0:2])

    img = cv2.copyMakeBorder(img, top, bottom, left, right, cv2.BORDER_CONSTANT, value=[0, 0, 0])

    img = cv2.resize(img, (h, w))

    return img



def relight(imgsrc, alpha=1, bias=0):

    '''relight'''

    imgsrc = imgsrc.astype(float)

    imgsrc = imgsrc * alpha + bias

    imgsrc[imgsrc < 0] = 0

    imgsrc[imgsrc > 255] = 255

    imgsrc = imgsrc.astype(np.uint8)

    return imgsrc



def getfacefromcamera(outdir):

    createdir(outdir)

    camera = cv2.VideoCapture(0)

    haar = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')

    # haar.load('D:\opencv330\sources\data\haarcascades/haarcascade_frontalface_default.xml')

    n = 1

    while 1:

        if (n <= 200):

            print('It`s processing %s image.' % n)

            # 读帧

            success, img = camera.read()



            gray_img = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

            faces = haar.detectMultiScale(gray_img, 1.3, 5)

            for f_x, f_y, f_w, f_h in faces:

                face = img[f_y:f_y+f_h, f_x:f_x+f_w]

                face = cv2.resize(face, (IMGSIZE, IMGSIZE))

                #could deal with face to train

                face = relight(face, random.uniform(0.5, 1.5), random.randint(-50, 50))

                cv2.imwrite(os.path.join(outdir, str(n)+'.jpg'), face)



                cv2.putText(img, 'fetch data', (f_x, f_y - 20), cv2.FONT_HERSHEY_SIMPLEX, 1, 255, 2)  #显示名字

                img = cv2.rectangle(img, (f_x, f_y), (f_x + f_w, f_y + f_h), (255, 0, 0), 2)

                n+=1

            cv2.imshow('FDR', img)

            key = cv2.waitKey(30) & 0xff

            if key == 27:

                break

        else:

            break

    camera.release()

    cv2.destroyAllWindows()



if __name__ == '__main__':

    name = input('please input yourename: ')

    getfacefromcamera(os.path.join(r'C:\Users\liuping\PycharmProjects\study_opencv/trainfaces', name))

OpenCV(3.4.1) Error: Assertion failed (!empty()) in cv::CascadeClassifier::detectMultiScale, file C:\projects\opencv-python\opencv\modules\objdetect\src\cascadedetect.cpp, line 1698

Traceback (most recent call last):

  File "C:/Users/liuping/PycharmProjects/study_opencv/opencv.py", line 81, in <module>

    getfacefromcamera(os.path.join(r'C:\Users\liuping\PycharmProjects\study_opencv/trainfaces', name))

  File "C:/Users/liuping/PycharmProjects/study_opencv/opencv.py", line 59, in getfacefromcamera

    faces = haar.detectMultiScale(gray_img, 1.3, 5)

cv2.error: OpenCV(3.4.1) C:\projects\opencv-python\opencv\modules\objdetect\src\cascadedetect.cpp:1698: error: (-215) !empty() in function cv::CascadeClassifier::detectMultiScale

这个到底是哪里出的问题呢？

作者借鉴了一个相似问题的博客解决了这个问题，注意一下下面的代码：

haar = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')

这个代码的下面缺少对opencv分类器部分的path，可以加上下面这句解决：

haar.load('D:\opencv330\sources\data\haarcascades/haarcascade_frontalface_default.xml')

这里注意一定要按照opencv路径找到自己电脑的分类器path。

参考引用

https://blog.csdn.net/serena9636/article/details/52530446

https://www.jianshu.com/p/f4344669c694