I just want to capture one frame, save it to test.png and then exit the code.
In this program exit() doesn't work, I have to use CTRL+C from the terminal every time.
import cv2
#cv2.namedWindow("window")
cap = cv2.VideoCapture(0)
if cap.isOpened(): # if we are able to capture the first frame.
val, frame = cap.read()
else:
val = False
while val:
#cv2.imshow("window", frame)
cv2.imwrite('test.png',frame)
val, frame = cap.read()
key = cv2.waitKey(20)
if key == 27: # exit on ESC
break
cap.release
cv2.destroyAllWindows()
exit()
Thanks in advance.
cv::waitKey only works if any openCV window is present and maybe active.
Since you commented #cv2.namedWindow("window") and #cv2.imshow("window", frame) out there is no waitKey time and no chance to fetch the key.
Does it work if you activate namedWindow and imshow?
To be sure additionally try
if key > 0: # exit on ESC
break
to cancel on ANY keypress (but you still need an active openCV window)
To capture a single frame try this:
import cv2
cap = cv2.VideoCapture(0)
val = False
maxTry = 100 # maximum number of tries to capture a frame from an opened device
cTry = 0
if cap.isOpened(): # if we are able to capture the first frame.
while (!val) and (cTry < maxTry)
val, frame = cap.read()
cTry = cTry + 1
else:
val = False
if val:
cv2.imwrite('test.png',frame)
else:
print "No image captured"
cap.release
exit()
I am not a python programmer so please forgive me any syntax errors (and give me a hint to correct them)
The method waitkey(t) waits t in milliseconds, so your code is waiting 20 ms for a key press for each loop. Considering that your
cv2.imwrite('test.png',frame)
might take some time to write to file, are you perhaps pressing your exiting key at the wrong moment?
Try adding & 0xFF to the wait key:
key = cv2.waitKey(20) & 0xFF
You also need an active window:
Note
The function only works if there is at least one HighGUI window created and the window is active. If there are several HighGUI windows, any of them can be active.
for python3
cv2.imshow('imafast', frame)
if cv2.waitKey(25) & 0xFF == ord('q'):
break
Related
I'm trying to read a video, put some shapes on it and write it out using opencv-python (using VideoWriter class):
def Mask_info(path):
"""This function will mask the information part of the video"""
video = cv.VideoCapture(path)
framenum = video.get(cv.CAP_PROP_FRAME_COUNT)
fps = video.get(cv.CAP_PROP_FPS)
fourcc = cv.VideoWriter_fourcc(*"vp09")
width = int(video.get(cv.CAP_PROP_FRAME_WIDTH))
height = int(video.get(cv.CAP_PROP_FRAME_HEIGHT))
size = (width,height)
if (video.isOpened ==False ):
print("Error while reading the file.")
result = cv.VideoWriter("masked_video.mp4",fourcc,fps,size)
while(True):
isTrue,frame = video.read()
cv.rectangle(frame,(65,0),(255,10),(0,0,0),-1)
cv.rectangle(frame,(394,0),(571,10),(0,0,0),-1)
if isTrue == True:
result.write(frame)
cv.imshow("Masked Video",frame)
if cv.waitKey(1) & 0xFF == ord("d"):
break
else:
break
video.release()
result.release()
cv.destroyAllWindows()
Mask_info("samplesound.webm")
The problem is that the output video length is zero, while the input video is 10 seconds.
To elaborate on my comment above:
You should verify that video.read() returns any valid frame.
It could be that due to path or other issue the VideoCapture failed to open the input file.
You attempt to draw the rectangles (using cv.rectangle) before the if that checks whether you have a valid frame.
But if video.read() failed (e.g. when reaching the end of the input) frame will be None. Then cv.rectangle will throw an exception causing the program to terminate without flushing and closing the output file.
Instead you should do the drawings inside the isTrue == True branch of the if:
if isTrue == True:
cv.rectangle(frame,(65,0),(255,10),(0,0,0),-1)
cv.rectangle(frame,(394,0),(571,10),(0,0,0),-1)
result.write(frame)
# ...
I have a camera that faces an LED sensor that I want to restrict on capturing images when the object is in sight otherwise not capturing. I will designate a point or region where the color pixels will change as an object arrives it will wait for 3sec and then capture. Thereafter it will not capture the same object if it still remains in the designated region. Here are my codes.
import cv2
import numpy as np
import os
os.chdir('C:/Users/Man/Desktop')
previous_flag = 0
current_flag = 0
a = 0
video = cv2.VideoCapture(0)
while True:
ret, frame = video.read()
rgb = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
cv2.imshow('Real Time', rgb)
cv2.waitKey(1)
if(rgb[400, 200, 0]>200): # selecting a point that will change in terms of pixel values
current_flag = 0
previous_flag = current_flag
print('No object Detected')
else: # object arrived
current_flag = 1
change_in_flags = current_flag - previous_flag
if(change_in_flags==1):
time.sleep(3)
cv2.imwrite('.trial/cam+str(a).jpg', rgb)
a += 1
previous_flag = current_flag
video.release()
cv2.destroyAllWindows()
When I implement the above program, for the first case (if) it prints several lines of No object Detected.
How can I reduce those sequentially printed lines for No object Detected statement? So that the program can just print one line without repetition.
I also tried to add a while loop to keep the current status true after a+=1 like:
while True:
previous_flag = current_flag
continue
It worked but the system became so slow is there any way to avoid such a while loop such that the system becomes faster? Any advice on that
import cv2
import numpy as np
import os
os.chdir('C:/Users/Man/Desktop')
state1=0
a = 0
video = cv2.VideoCapture(0)
while True:
ret, frame = video.read()
rgb = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
cv2.imshow('Real Time', rgb)
cv2.waitKey(1)
if(rgb[400, 200, 0]>200): # selecting a point that will change in terms of pixel values
if(state1 == 0):
print('No object Detected')
state1=1
else: # object arrived
time.sleep(1)
if(state1==1)
print('Object is detected')
cv2.imwrite('./trial/cam+str(a).jpg', rgb)
a += 1
state1=0
video.release()
cv2.destroyAllWindows()
I am running a Camera Calibration program from Python using openCV. I am using my computer camera from an XPS 15 9575 in order to capture different frames of a classic black and white checkerboard that I printed. For some reason, it never registers in the program that there is a checkerboard.
I've run this program by itself and with already produced images and it works. It only doesn't work as I try to capture new ones and process them instantly.
This is the beginning of the code. It runs to check to see if it finds the corners and then moves onto the next step. When running, it never makes it past this.
cam = cv2.VideoCapture(0)
cv2.namedWindow("test")
img_counter = 0
imgNames = []
size = (5,5)
while True:
ret, frame = cam.read()
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
cv2.imshow("test", gray)
if not ret:
break
k = cv2.waitKey(1)
if k%256 == 27:
break
elif k%256 == 32:
img_name = "{}.png".format(img_counter)
imgtemp = cv2.imread(img_name)
graytemp = cv2.cvtColor(imgtemp,cv2.COLOR_BGR2GRAY)
ret, corners = cv2.findChessboardCorners(graytemp, size,None)
print (ret)
if ret == True:
print ("good!")
imgNames.append(img_name)
cv2.imwrite(img_name, frame)
img_counter += 1
else:
print ("again")
In your code above, you are trying to read an image which actually doesn't exist. See these lines:
img_name = "{}.png".format(img_counter)
imgtemp = cv2.imread(img_name)
Here, img_name is just a string, which doesn't point to an image file yet. You can do one thing, capture a frame and save it here and give it a name img_name and then try to read it via cv2.imread function, like below:
img_name = "{}.png".format(img_counter)
cv2.imwrite(img_name, frame)
imgtemp = cv2.imread(img_name)
Alternatively, you can replace imgtemp = cv2.imread(img_name) with imgtemp = frame. In this case, you don't have to save and then process a frame. Here, once a spacebar is pressed, processing is done on the current captured video frame without saving it.
And don't forget to add below lines at the end of your code:
cam.release()
cv2.destroyAllWindows()
Aim : Detect the motion and save only the motion periods in files with names of the starting time.
Now I met the issue about how to save the video to the files with video starting time.
What I tested :
I tested my program part by part. It seems that each part works well except the saving part.
Running status: No error. But in the saving folder, there is no video. If I use a static saving path instead, the video will be saved successfully, but the video will be override by the next video. My codes are below:
import cv2
import numpy as np
import time
cap = cv2.VideoCapture( 0 )
bgst = cv2.createBackgroundSubtractorMOG2()
fourcc=cv2.VideoWriter_fourcc(*'DIVX')
size = (int(cap.get(cv2.CAP_PROP_FRAME_WIDTH)), int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT)))
n = "start_time"
while True:
ret, frame = cap.read()
dst = bgst.apply(frame)
dst = np.array(dst, np.int8)
if np.count_nonzero(dst)>3000: # use this value to adjust the "Sensitivity“
print('something is moving %s' %(time.ctime()))
path = r'E:\OpenCV\Motion_Detection\%s.avi' %n
out = cv2.VideoWriter( path, fourcc, 50, size )
out.write(frame)
key = cv2.waitKey(3)
if key == 32:
break
else:
out.release()
n = time.ctime()
print("No motion Detected %s" %n)
What I meant is:
import cv2
import numpy as np
import time
cap = cv2.VideoCapture( 0 )
bgst = cv2.createBackgroundSubtractorMOG2()
fourcc=cv2.VideoWriter_fourcc(*'DIVX')
size = (int(cap.get(cv2.CAP_PROP_FRAME_WIDTH)),int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT)))
path = r'E:\OpenCV\Motion_Detection\%s.avi' %(time.ctime())
out = cv2.VideoWriter( path, fourcc, 16, size )
while True:
ret, frame = cap.read()
dst = bgst.apply(frame)
dst = np.array(dst, np.int8)
for i in range(number of frames in the video):
if np.count_nonzero(dst)<3000: # use this value to adjust the "Sensitivity“
print("No Motion Detected")
out.release()
else:
print('something is moving %s' %(time.ctime()))
#label each frame you want to output here
out.write(frame(i))
key = cv2.waitKey(1)
if key == 32:
break
cap.release()
cv2.destroyAllWindows()
If you see the code there will be a for loop, within which the process of saving is done.
I do not know the exact syntax involving for loop with frames, but I hope you have the gist of it. You have to find the number of frames present in the video and set that as the range in the for loop.
Each frame gets saved uniquely (see the else condition.) As I said I do not know the syntax. Please refer and follow this procedure.
Cheers!
My current mode of recording video using opencv looks something like this
import cv
capture=cv.CaptureFromCAM(self.deviceID)
img_size=cv.GetSize(cv.QueryFrame(capture))
#create a writer object for the video
writer=cv.CreateVideoWriter(
filename='temp.avi',
fourcc=cv.CV_FOURCC('M','J','P','G'),
fps=15,
frame_size=img_size,
is_color=1)
while True:
#grab the frame
img=cv.QueryFrame(capture)
#write frame to video
cv.WriteFrame(writer,img)
#if 'Enter' or 'Esc' key is pressed, end video capture
c = cv.WaitKey(7) % 0x100
if c == 27 or c == 10:
break
The problem is that I have to manually set the frames per second in advance. I've storing the images in a list and keeping track of how much time has elapsed, but that just exports a file with no frames:
import cv
import time
capture=cv.CaptureFromCAM(self.deviceID)
img_size=cv.GetSize(cv.QueryFrame(capture))
imgList=[]
zero=time.time()
while True:
#grab the frame
img=cv.QueryFrame(capture)
imgList.append(img)
cv.ShowImage("Window1",img)
#if 'Enter' or 'Esc' key is pressed, end video capture
c = cv.WaitKey(7) % 0x100
if c == 27 or c == 10:
break
duration=time.time()-zero
framesPerSecond=len(imgList)/duration)
writer=cv.CreateVideoWriter(
filename='temp.avi',
fourcc=cv.CV_FOURCC('M','J','P','G'),
fps=framesPerSecond,
frame_size=img_size,
is_color=1)
for i in imgList:
cv.writeFrame(writer,i)
A little stucks. Any suggestions on an alternative method or tweaks to my existing code would be greatly helpful.