OpenCV Python - How to use current screen as source image?-CodePudding

I am trying to draw a red square around a picture whenever it appears on my screen. I'm using python 3.7. This is my first day with opencv, so the code I have so far is extremely clunky.

import cv2
import numpy
from mss import mss

template = cv2.imread("mountain.png")
template = cv2.cvtColor(template, cv2.COLOR_BGR2GRAY)
img = numpy.array(sct.grab(monitor))
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
# perform match
res = cv2.matchTemplate(gray,template ,cv2.TM_CCOEFF)
# get coordinates of best match
min_val, max_val, min_loc, max_loc = cv2.minMaxLoc(res)
top_left = min_loc
bottom_right = (top_left[0]   w, top_left[1]   h)
# draw red rectangle over original screen capture
cv2.rectangle(img,top_left, bottom_right,(0,0,255),3)
# display image
#cv2.imshow('Result',img)

I get the following error:

error                                     Traceback (most recent call last)
/var/folders/ks/mmylcnjn1cjdthv824f0l36h0000gn/T/ipykernel_7719/1707960325.py in <module>
     10 gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
     11 # perform match
---> 12 res = cv2.matchTemplate(gray,template ,cv2.TM_CCOEFF)
     13 # get coordinates of best match
     14 min_val, max_val, min_loc, max_loc = cv2.minMaxLoc(res)

error: OpenCV(3.4.2) /opt/concourse/worker/volumes/live/9523d527-1b9e-48e0-7ed0-a36adde286f0/volume/opencv-suite_1535558719691/work/modules/imgproc/src/templmatch.cpp:1107: error: (-215:Assertion failed) _img.size().height <= _templ.size().height && _img.size().width <= _templ.size().width in function 'matchTemplate'

If I'm reading this right, then the problem is that I am trying to compare the template image which is bigger than the source image. However, I can't figure out how to solve this because the screen capture is definitely bigger than the image.

CodePudding user response：

This error shows when either,path of the image is wrong or name of the image is wrong. you can print your images for checking.

CodePudding user response：

This was a dumb mistake. But in case anybody is wondering, I needed to insert the following before the code:

with mss() as sct: monitor = sct.monitors[1]