Python 用opencv捕获单张图片
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Capture single picture with opencv
提问by a sandwhich
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 opencv?
我已经看到了一些关于使用 python 和 opencv 从网络摄像头流捕获帧的事情，但是如何使用 python 和 opencv 仅以指定的分辨率捕获一张图片？
回答by meduz
Use SetCaptureProperty :
使用 SetCaptureProperty ：
import cv
capture = 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.
不知道如何关闭相机，虽然。
Example of a ipython session with the above code :
使用上述代码的 ipython 会话示例：
In [1]: import cv
In [2]: capture = cv.CaptureFromCAM(0)
In [7]: img = cv.QueryFrame(capture)
In [8]: print img.height, img.width
480 640
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
240 320
回答by akshaynagpal
You can capture a single frame by using the VideoCapturemethod of OpenCV.
您可以使用VideoCaptureOpenCV的方法捕获单个帧。
import numpy as np
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 image
if 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.
稍后您可以使用PIL轻松修改分辨率。
回答by Sreeragh A R
import cv2
cap = cv2.VideoCapture(0)
cap.set(3,640) #width=640
cap.set(4,480) #height=480
if cap.isOpened():
_,frame = cap.read()
cap.release() #releasing camera immediately after capturing picture
if _ and frame is not None:
cv2.imwrite('img.jpg', frame)
cv2.imwrite(name, frame)
