Capture Single Picture With Opencv

I have seen several things about capturing frames from a webcam stream using python and opencv, But how do you capture only one picture at a specified resolution with python and op

Solution 1:

You can capture a single frame by using the VideoCapture method of OpenCV.

import cv2

cap = cv2.VideoCapture(0) # video capture source camera (Here webcam of laptop) 
ret,frame = cap.read() # return a single frame in variable `frame`while(True):
    cv2.imshow('img1',frame) #display the captured imageif cv2.waitKey(1) & 0xFF == ord('y'): #save on pressing 'y' 
        cv2.imwrite('images/c1.png',frame)
        cv2.destroyAllWindows()
        break

cap.release()

Later you can modify the resolution easily using PIL.

Solution 2:

Use SetCaptureProperty :

importcvcapture= cv.CaptureFromCAM(0)
cv.SetCaptureProperty(capture, cv.CV_CAP_PROP_FRAME_HEIGHT, my_height)
cv.SetCaptureProperty(capture, cv.CV_CAP_PROP_FRAME_WIDTH, my_width)
cv.SetCaptureProperty(capture, cv.CV_CAP_PROP_FORMAT, cv.IPL_DEPTH_32F)

img = cv.QueryFrame(capture)

Do not know how to close the camera, though.

Example of a ipython session with the above code :

In [1]: import cv

In [2]: capture = cv.CaptureFromCAM(0)

In [7]: img = cv.QueryFrame(capture)

In [8]: print img.height, img.width
480640

In [9]: cv.SetCaptureProperty(capture, cv.CV_CAP_PROP_FRAME_HEIGHT, 480/2)
Out[9]: 1

In [10]: cv.SetCaptureProperty(capture, cv.CV_CAP_PROP_FRAME_WIDTH, 640/2)
Out[10]: 1

In [11]: img = cv.QueryFrame(capture)

In [12]: print img.height, img.width
240320

Solution 3:

import cv2
cap = cv2.VideoCapture(0)
cap.set(3,640) #width=640
cap.set(4,480) #height=480if cap.isOpened():
    _,frame = cap.read()
    cap.release() #releasing camera immediately after capturing pictureif _ and frame isnotNone:
        cv2.imwrite('img.jpg', frame)
        cv2.imwrite(name, frame)