How to read a mouse left click event in python?

asked 2018-04-10 01:22:32 -0500

masterenol gravatar image

updated 2018-04-10 02:28:15 -0500

For example, I would like to make a code like this:

while True:
[...]

   if <left mouse button is clicked>:
      print("Left Mouse has been clicked")

[...]

cv2.destroyAllWindows

I've read the "Mouse as a Paint-Brush", but it does not explain how to have Python only recognize the mouse left click event.

I'd appreciate any help I can get.

I'd tried modifying the code from the tutorial to suit my needs, but I can't seem to get the code to work:

def mouse(event,x,y,flags,param):
    if event == cv2.EVENT_LBUTTONDBLCLK:
        return True

[...]
cap = cv2.VideoCapture(0)

while True:
    [...]
    if cv2.setMouseCallback('frame', mouse)==True:
      print("Left Mouse Button has been clicked")
    [...]

cv2.destroyAllWindows

[Update]

I managed make progress by using the following code I modified from the more advanced example on the "Mouse as a Paint-Brush" tutorial. I modified the code for the purpose of having OpenCV recognize a mouse left-button click on a live webcam:

[...]
cap = cv2.VideoCapture(0)
drawing = False

def draw_circle(event,x,y,flags,param)
   global drawing
   if event == cv2.EVENT_LBUTTONDBCLK:
      drawing = True

while True:
  [...]
  drawing = False
  cv2.setMouseCallback('frame',draw_circle)

  if drawing == True:
     print("Left Mouse Button has been clicked.")
  [...]

cv2.destroyAllWindows
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Comments

it's even in the tutorial. you didn't look at all.

berak gravatar imageberak ( 2018-04-10 01:24:55 -0500 )edit

berak, I did read the tutorial. I'm modifying the code in the tutorial to make it work according to my needs. This code does not work:

def mouse(event,x,y,flags,param): if event == cv2.EVENT_LBUTTONDBLCLK: return True [...] cap = cv2.VideoCapture(0) while True: [...] if cv2.setMouseCallback('frame', mouse)==True print("Left Mouse Button has been clicked") [...] cv2.destroyAllWindows

I've been struggling with this for a while, and I don't appreciate being accused of lying.

masterenol gravatar imagemasterenol ( 2018-04-10 01:45:19 -0500 )edit

cmon, the tutorial lists all events, and it uses LBUTTONDOWN a few lines later.

" I don't appreciate being accused of lying." -- well, oh.

berak gravatar imageberak ( 2018-04-10 01:52:27 -0500 )edit

doesn't the "more advanced" example there do, what you want ?

berak gravatar imageberak ( 2018-04-10 01:57:21 -0500 )edit

Not quite. I needed the code to work while using live video capture. I made progress by adding 'drawing = False' followed by 'cv2.setMouseCallback('frame',draw_circle)' inside the while loop for the webcam video.

masterenol gravatar imagemasterenol ( 2018-04-10 02:31:10 -0500 )edit

maybe it's easier to process your event inside the handler.

but if you want to process it in the main loop, you'lll have to set a flag on LBUTTONDOWN, and reset it on LBUTTONUP.

it's more a general logig problem, not an opencv one.

berak gravatar imageberak ( 2018-04-10 02:40:03 -0500 )edit