Screen Capture with OpenCV and Python-2.7

问题:

I'm using Python 2.7 and OpenCV 2.4.9.

I need to capture the current frame that is being shown to the user and load it as an cv::Mat object in Python.

Do you guys know a fast way to do it recursively?

I need something like what's done in the example below, that captures Mat frames from a webcam recursively:

import cv2

cap = cv2.VideoCapture(0)
while(cap.isOpened()):
    ret, frame = cap.read()
    cv2.imshow('WindowName', frame)
    if cv2.waitKey(25) & 0xFF == ord('q'):
        cap.release()
        cv2.destroyAllWindows()
        break

In the example it's used the VideoCapture class to work with the captured image from the webcam.

With VideoCapture.read() a new frame is always being readed and stored into a Mat object.

Could I load a "printscreens stream" into a VideoCapture object? Could I create a streaming of my computer's screen with OpenCV in Python, without having to save and delete lots of .bmp files per second?

I need this frames to be Mat objects or NumPy arrays, so I can perform some Computer Vision routines with this frames in real time.

回答1:

That's a solution code I've written using @Raoul tips.

I used PIL ImageGrab module to grab the printscreen frames.

import numpy as np
from PIL import ImageGrab
import cv2

while(True):
    printscreen_pil =  ImageGrab.grab()
    printscreen_numpy =   np.array(printscreen_pil.getdata(),dtype='uint8')\
    .reshape((printscreen_pil.size[1],printscreen_pil.size[0],3)) 
    cv2.imshow('window',printscreen_numpy)
    if cv2.waitKey(25) & 0xFF == ord('q'):
        cv2.destroyAllWindows()
        break

回答2:

I had frame rate problems with other solutions, mss solve them.

import numpy as np
import cv2
from mss import mss
from PIL import Image

mon = {'top': 160, 'left': 160, 'width': 200, 'height': 200}

sct = mss()

while 1:
    sct.get_pixels(mon)
    img = Image.frombytes('RGB', (sct.width, sct.height), sct.image)
    cv2.imshow('test', np.array(img))
    if cv2.waitKey(25) & 0xFF == ord('q'):
        cv2.destroyAllWindows()
        break