Face Detection

Do I see human faces? How many? Where?

Getting Started

Using Angus python SDK:

# -*- coding: utf-8 -*-
import angus.client
from pprint import pprint

conn = angus.client.connect()
service = conn.services.get_service('face_detection', version=1)
job = service.process({'image': open('./macgyver.jpg', 'rb')})
pprint(job.result)

Input

The API takes a stream of 2d still images as input, of format jpg or png, without constraints on resolution.

Note however that the bigger the resolution, the longer the API will take to process and give a result.

The function process() takes a dictionary as input formatted as follows:

{'image' : file}
  • image: a python File Object as returned for example by open() or a StringIO buffer.

Output

Events will be pushed to your client following that format:

{
  "input_size" : [480, 640],
  "nb_faces" : 2,
  "faces" : [
              {
                "roi" : [345, 223, 34, 54],
                "roi_confidence" : 0.89
              },
              {
                "roi" : [35, 323, 45, 34],
                "roi_confidence" : 0.56
              }
            ]
}
  • input_size : width and height of the input image in pixels (to be used as reference to roi output.
  • nb_faces : number of faces detected in the given image
  • roi : contains [pt.x, pt.y, width, height] where pt is the upper left point of the rectangle outlining the detected face.
  • roi_confidence : an estimate of the probability that a real face is indeed located at the given roi.

Code Sample

requirements: opencv2, opencv2 python bindings

This code sample retrieves the stream of a web cam and display in a GUI the result of the face_detection service.

# -*- coding: utf-8 -*-
import cv2
import numpy as np
import StringIO

import angus.client

def main(stream_index):
    camera = cv2.VideoCapture(stream_index)
    camera.set(cv2.cv.CV_CAP_PROP_FRAME_WIDTH, 640)
    camera.set(cv2.cv.CV_CAP_PROP_FRAME_HEIGHT, 480)
    camera.set(cv2.cv.CV_CAP_PROP_FPS, 10)

    if not camera.isOpened():
        print("Cannot open stream of index {}".format(stream_index))
        exit(1)

    print("Video stream is of resolution {} x {}".format(camera.get(3), camera.get(4)))

    conn = angus.client.connect()
    service = conn.services.get_service("age_and_gender_estimation", version=1)
    service.enable_session()

    while camera.isOpened():
        ret, frame = camera.read()

        if not ret:
            break

        gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
        ret, buff = cv2.imencode(".jpg", gray,  [cv2.IMWRITE_JPEG_QUALITY, 80])
        buff = StringIO.StringIO(np.array(buff).tostring())

        job = service.process({"image": buff})
        res = job.result

        for face in res['faces']:
            x, y, dx, dy = face['roi']
            cv2.rectangle(frame, (x, y), (x+dx, y+dy), (0,255,0))

        cv2.imshow('original', frame)
        if cv2.waitKey(1) & 0xFF == ord('q'):
            break

    service.disable_session()

    camera.release()
    cv2.destroyAllWindows()

if __name__ == '__main__':
    ### Web cam index might be different from 0 on your setup.
    ### To grab a given video file instead of the host computer cam, try:
    ### main("/path/to/myvideo.avi")
    main(0)
../../_images/screenshot_facedetection.png