using open cv to control relay

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And your problem is...? What did you try? It seems that you didn't invest the minimal effort to solve this.

I'm lost as to how I should even start this project to be quite frank. I've been reading through all the tutorials I can find on open cv and it seems that everything is geared to capturing images and processing them, but not actually doing anything physical, if that makes sense. I want the program to be able to pick out either green, blue, or red colors. Then, once one of those colors is detected, send a signal to a relay to turn on a pump for a specified length of time. If you could just point me in the right direction I would greatly appreciate it!

I want to use open cv to be able to identify 3 colors: red blue, and green. and then when it detects those colors,

an image will be helpful to understand your need

@sturkmen. U don't needed images. Probably used webcam.

@Noob87. What ur pi model OS? R u using webcam or picamera?

I do not have relay switch. I can substitute for leds

I'm sorry, I should have been more clear. I'm using a raspberry pi4 and a picamera. I have been able to alter code to pick up the three colors I need. I guess now my question is how do I get the program once it finds a color (say blue) to send a signal to the GPIO pins to turn on my relay for the pump? Once the program finds a color, is that stored as a variable which can be used to send such signal? I'm really confused. Thanks again everyone for your time.

I am using pi4 with 4gb/8gb, Buster v10. Thonny 3.7.3. I posted my answer detected blue colour. Notitced, I used 5% for 100 and 105. If ur colour is slightly than my. U can in increasing 10% to make sure rectangle doesn't shaking.. Btw, I do no have the code with me.I'm off for a years.

With this:

if len(bluecnts)>0:
    blue_area = max(bluecnts, key=cv2.contourArea)
    (xg,yg,wg,hg) = cv2.boundingRect(blue_area)
    cv2.rectangle(frame,(xg,yg),(xg+wg, yg+hg),(0,255,0),2)
   #if rectangle is detected, then do something to set boolean to turn gpio on
   :
   :

Btw, u can used VideoCapturer api with picamera