Develop Reference

How to detect when a specific object moves out of frame in an opencv program?

I'm currently practicing opencv and tried the face recognition code and it's working fine. I'd like to get notified if I'm away from the screen for more than 2 mins. I'm trying to play an audio file when I'm away and stop it when I'm back.
import cv2 as cv
import sys
cascPath = sys.argv[1]
faceCascade = cv2.CascadeClassifier(cascPath)
video_capture = cv.VideoCapture(0)
while True:
# Capture frame-by-frame
ret, frame = video_capture.read()
gray = cv.cvtColor(frame, cv.COLOR_BGR2GRAY)
faces = faceCascade.detectMultiScale(
gray,
scaleFactor=1.1,
minNeighbors=5,
minSize=(30, 30),
flags=cv.CASCADE_SCALE_IMAGE
)
# Draw a rectangle around the faces
for (x, y, w, h) in faces:
cv.rectangle(frame, (x, y), (x+w, y+h), (0, 255, 0), 2)
# Display the resulting frame
cv.imshow('Video', frame)
# check if the tuple faces is empty
if len(faces) == 0:
start_time = time.time()
while len(faces) == 0:
print('person is away for ',time.time()-start_time)
d_time = time.time()
if d_time-start_time > 120:
pygame.mixer.init()
sound = pygame.mixer.Sound("Recording.mp3")
sound.play(5)
if cv.waitKey(1) & 0xFF == ord('q'):
break
video_capture.release()
cv.destroyAllWindows()

Detect timestamp of position of object detected from an mp4 video using OpenCV in Python

I am trying to detect objects from an mp4 video file using OpenCV in Python. I am able to detect the objects in the video.
I would like to get the timestamp of the position at which the object was detected in the video file and write it to a text file.
Here is my code so far:
import cv2
my_cascade = cv2.CascadeClassifier('toy.xml')
def detect(gray, frame):
toys= my_cascade.detectMultiScale(gray, 1.3, 5)
for (x, y, w, h) in toys:
cv2.rectangle(frame, (x, y), (x+w, y+h), (255, 0, 0), 2)
#Logic to write time stamp to file goes here
return frame
video_capture = cv2.VideoCapture('home.mp4')
cv2.startWindowThread()
while True:
_, frame = video_capture.read()
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
canvas = detect(gray, frame)
cv2.imshow('Video', canvas)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
video_capture.release()
cv2.destroyAllWindows()
I tried to use VideoCapture's method get() using property identifier like this:
video_capture.get(CV_CAP_PROP_POS_MSEC)
but get an error name 'CV_CAP_PROP_POS_MSEC' is not defined
Seems like cv2 does not have this method or property identifier implemented.
Is there any other way in cv2 to implement what I want?
Please help.
SOLVED
This will print timestamp of the position of object everytime it is detected in the video.
Here is the working code:
import cv2
my_cascade = cv2.CascadeClassifier('toy.xml')
def detect(gray, frame):
toys= my_cascade.detectMultiScale(gray, 1.3, 5)
for (x, y, w, h) in toys:
cv2.rectangle(frame, (x, y), (x+w, y+h), (255, 0, 0), 2)
print("Toy Detected at: "+str(video_capture.get(cv2.CAP_PROP_POS_MSEC)))
return frame
video_capture = cv2.VideoCapture('home.mp4')
cv2.startWindowThread()
while True:
_, frame = video_capture.read()
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
canvas = detect(gray, frame)
cv2.imshow('Video', canvas)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
video_capture.release()
cv2.destroyAllWindows()

cv2 does have the property implemented, but the full name needs to be used.
This should work
import cv2
my_cascade = cv2.CascadeClassifier('toy.xml')
def detect(gray, frame):
toys= my_cascade.detectMultiScale(gray, 1.3, 5)
for (x, y, w, h) in toys:
cv2.rectangle(frame, (x, y), (x+w, y+h), (255, 0, 0), 2)
#Logic to write time stamp to file goes here
return frame
video_capture = cv2.VideoCapture('home.mp4')
cv2.startWindowThread()
while True:
_, frame = video_capture.read()
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
canvas = detect(gray, frame)
print (video_capture.get(cv2.CAP_PROP_POS_MSEC))
cv2.imshow('Video', canvas)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
video_capture.release()
cv2.destroyAllWindows()
i.e. you want the property of the instance video_capture not the generic class VideoCapture and the property name is prefixed by the class cv2.. The property name is either CAP_PROP_POS_MSECor CV_CAP_PROP_MSEC - depending on the OpenCV version (see Can't get VideoCapture property as the property identifier are not defined ).

Saving image from live feed of detected faces

import cv2
import sys
faceCascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')
video_capture = cv2.VideoCapture(0)
while True:
# Capture frame-by-frame
ret, frame = video_capture.read()
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
faces = faceCascade.detectMultiScale(
gray,
scaleFactor=2.0,
minNeighbors=5,A minSize=(30, 30),
flags = 0
#flags=cv2.cv.CV_HAAR_SCALE_IMAGE
)
# Draw a rectangle around the faces
for (x, y, w, h) in faces:
cv2.rectangle(frame, (x, y), (x+w, y+h), (0, 255, 0), 2)
# Display the resulting frame
cv2.imshow('Video', frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
# Write frame in file
for (x, y, w, h) in faces:
cv2.rectangle(frame, (x, y), (x+w, y+h), (0, 255, 0), 2)
cv2.imwrite('only_face.jpg')
break
# When everything is done, release the capture
video_capture.release()
cv2.destroyAllWindows()
The above code is detecting faces from live feed of camera and saving image of only one face. i want to save image of multiple faces that are detected from the feed. It only saves image of one face

See what I have included here:
import cv2
import sys
faceCascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')
video_capture = cv2.VideoCapture(0)
increment = 0 #---Declare a variable that will increment for every image saved
while True:
# Capture frame-by-frame
ret, frame = video_capture.read()
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
faces = faceCascade.detectMultiScale(gray, scaleFactor=2.0, minNeighbors=5,A minSize=(30, 30), flags = 0
#flags=cv2.cv.CV_HAAR_SCALE_IMAGE
)
# Draw a rectangle around the faces
for (x, y, w, h) in faces:
cv2.rectangle(frame, (x, y), (x+w, y+h), (0, 255, 0), 2)
# Display the resulting frame
cv2.imshow('Video', frame)
increment = increment + 1 #--- Initiate the increment variable
if cv2.waitKey(1) & 0xFF == ord('q'):
# Write frame in file
for (x, y, w, h) in faces:
cv2.rectangle(frame, (x, y), (x+w, y+h), (0, 255, 0), 2)
cv2.imwrite('only_face' + str(increment) + '.jpg') #--- Here is where the increment variable is placed. It will be incremented for every face and thus saving every face that gets detected.
break
# When everything is done, release the capture
video_capture.release()
cv2.destroyAllWindows()
I have included the increment variable, which will be incremented for every face detected thus saving every image separately.

cv2.waitkey(1) not running in opencv python

I need to understand cv2.waitkey() in python with cv2
faceCascade = cv2.CascadeClassifier(cascPath)
video_capture = cv2.VideoCapture(0)
while True:
# Capture frame-by-frame
ret, frame = video_capture.read()
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
faces = faceCascade.detectMultiScale(
gray,
scaleFactor=1.1,
minNeighbors=8,
minSize=(40, 40),
#flags=cv2.cv.CV_HAAR_SCALE_IMAGE
flags = 0
)
# Draw a rectangle around the faces
for (x, y, w, h) in faces:
cv2.rectangle(gray, (x, y), (x+w, y+h), (0, 255, 0), 2)
# Display the resulting frame
cv2.imshow('Video', gray)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
if cv2.waitKey(1) & 0xFF == ord('b'):
cv2.imwrite('example.png',gray)
cv2.waitKey() when I press b it doesn't save picture but press q works . Please help!

You are calling waitKey() twice. With your code, press any key but q then press b and it will save the image.
Only call waitKey(1) once, and save the result in a variable, then test that variable, e.g.:
keypress = cv2.waitKey(1)
if keypress & 0xFF == ord('q'):
break
if keypress & 0xFF == ord('b'):
cv2.imwrite('example.png',gray)

python 2.7 and opencv code gives cvtcolor error

faceCascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')
video_capture = cv2.VideoCapture(0)
while True:
ret, frame = video_capture.read()
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
faces = faceCascade.detectMultiScale(
frame,
scaleFactor=1.1,
minNeighbors=5,
minSize=(30, 30),
flags=cv2.cv.CV_HAAR_SCALE_IMAGE
)
# Draw a rectangle around the faces
for (x, y, w, h) in faces:
cv2.rectangle(frame, (x, y), (x+w, y+h), (0, 255, 0), 2)
# Display the resulting frame
cv2.imshow('Video', frame)
if cv2.waitKey(1)==ord('e'):
break
code gives this error, please help me
Traceback (most recent call last): File
"C:\Users\yavuz\Desktop\sor\sor2.pyw", line 15, in
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY) error: ........\opencv\modules\imgproc\src\color.cpp:3737: error: (-215)
scn == 3 || scn == 4 in function cv::cvtColor

You need to check if "ret == True' before going on with cvtColor. The code should look like this:
faceCascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')
video_capture = cv2.VideoCapture(0)
while True:
ret, frame = video_capture.read()
if ret == True:
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
faces = faceCascade.detectMultiScale(
frame,
scaleFactor=1.1,
minNeighbors=5,
minSize=(30, 30),
flags=cv2.cv.CV_HAAR_SCALE_IMAGE
)
# Draw a rectangle around the faces
for (x, y, w, h) in faces:
cv2.rectangle(frame, (x, y), (x+w, y+h), (0, 255, 0), 2)
# Display the resulting frame
cv2.imshow('Video', frame)
if cv2.waitKey(1)==ord('e'):
break