CODEWITHSUNDEEP
pythonopencv
L.Jovi
L.Jovi

Reputation: 1751

how to correctly use peopledetect.py in opencv?

I'm newbie of opencv and I have real need for detecting people/human within some images, I find python interface named peopledetect.py and I look through code just like this..

#!/usr/bin/env python

import numpy as np
import cv2

help_message = '''
USAGE: peopledetect.py <image_names> ...

Press any key to continue, ESC to stop.
'''

def inside(r, q):
    rx, ry, rw, rh = r
    qx, qy, qw, qh = q
    return rx > qx and ry > qy and rx + rw < qx + qw and ry + rh < qy + qh

def draw_detections(img, rects, thickness = 1):
    for x, y, w, h in rects:
        # the HOG detector returns slightly larger rectangles than the real objects.
        # so we slightly shrink the rectangles to get a nicer output.
        pad_w, pad_h = int(0.15*w), int(0.05*h)
        cv2.rectangle(img, (x+pad_w, y+pad_h), (x+w-pad_w, y+h-pad_h), (0, 255, 0), thickness)


if __name__ == '__main__':
    import sys
    from glob import glob
    import itertools as it

    print help_message

    hog = cv2.HOGDescriptor()
    hog.setSVMDetector( cv2.HOGDescriptor_getDefaultPeopleDetector() )

    for fn in it.chain(*map(glob, sys.argv[1:])):
        print fn, ' - ',
        try:
            img = cv2.imread(fn)
        except:
            print 'loading error'
            continue

        found, w = hog.detectMultiScale(img, winStride=(8,8), padding=(32,32), scale=1.05)
        found_filtered = []
        for ri, r in enumerate(found):
            for qi, q in enumerate(found):
                if ri != qi and inside(r, q):
                    break
            else:
                found_filtered.append(r)
        draw_detections(img, found)
        draw_detections(img, found_filtered, 3)
        print '%d (%d) found' % (len(found_filtered), len(found))
        cv2.imshow('img', img)
        ch = 0xFF & cv2.waitKey()
        if ch == 27:
            break
    cv2.destroyAllWindows()

To be honest, I don't really understand principle of HOG.

I prepare some image from opencv website and try to do some basic test by using this code, maybe like this..

$ ./peopledetect.py abba.png
$ ./peopledetect.py luna.jpg

but I don't see any retangle drawed within code on display, maybe I did wrong.. could someone help me? thanks so much..

abba.pngluan.jpg

Upvotes: 2

Views: 5936

Answers (1)

DrMcCleod
DrMcCleod

Reputation: 4053

This code is using OpenCV's implementation of the HOG detector, see this tutorial for a good explanation of the algorithm. This classifier is trained on whole body images of people standing more or less upright, and that is what it will detect. If you want to detect people when you can see their face, but not the whole of their body, then take a look at OpenCV's face detection algorithms instead.

Upvotes: 3

Related Questions