OpenCV 人脸检测（一）

import cv2
import numpy as np
from matplotlib import pyplot as plt


def detect(filename):
    img = cv2.imread(filename)
    gray =cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    
    #检测正脸
    front_face_cascade = cv2.CascadeClassifier('./cascades/haarcascade_frontalface_default.xml')
    faces0 = front_face_cascade.detectMultiScale(gray, 1.022, 5)
    print("共检测到%d张人的正脸" %len(faces0))
    
    #检测侧脸
    profile_face_cascade = cv2.CascadeClassifier('./cascades/haarcascade_profileface.xml')
    faces1 = profile_face_cascade.detectMultiScale(gray, 1.2, 6)
    print("共检测到%d张人的侧脸" %len(faces1))
   
    for (x, y, w, h) in faces0:
        cv2.rectangle(img, (x,y), (x+w,y+h), (0,0,255), 1) #画红色矩形框标记正脸
    for (x, y, w, h) in faces1:
        cv2.rectangle(img, (x,y), (x+w,y+h), (0,255,0), 1) #画绿色矩形框标记侧脸
    return img

img = detect("physicists.jpg")
plt.subplot(1,1,1)
plt.imshow(cv2.cvtColor(img, cv2.COLOR_BGR2RGB))
plt.title("OpenCV 人脸检测",fontSize =16, color="b")
plt.show()

'''
detectMultiScale(...) method of cv2.CascadeClassifier instance
    detectMultiScale(image[, scaleFactor[, minNeighbors[, flags[, minSize[, maxSize]]]]]) -> objects
    .   @brief Detects objects of different sizes in the input image. The detected objects are returned as a list
    .   of rectangles.
    .  
    .   @param image Matrix of the type CV_8U containing an image where objects are detected.
    .   @param objects Vector of rectangles where each rectangle contains the detected object, the
    .   rectangles may be partially outside the original image.
    .   @param scaleFactor Parameter specifying how much the image size is reduced at each image scale.
    .   @param minNeighbors Parameter specifying how many neighbors each candidate rectangle should have
    .   to retain it.
    .   @param flags Parameter with the same meaning for an old cascade as in the function
    .   cvHaarDetectObjects. It is not used for a new cascade.
    .   @param minSize Minimum possible object size. Objects smaller than that are ignored.
    .   @param maxSize Maximum possible object size. Objects larger than that are ignored. If `maxSize == minSize` model is evaluated on single scale.
    .  
    .   The function is parallelized with the TBB library.
    .  
    .   @note
    .   -   (Python) A face detection example using cascade classifiers can be found at
    .   opencv_source_code/samples/python/facedetect.py
'''