python-2.7opencvmouse

Opencv: detect mouse position clicking over a picture


I have this code in which I simply display an image using OpenCV:

    import numpy as np 
    import cv2

    class LoadImage:
        def loadImage(self):
            self.img=cv2.imread('photo.png')
            cv2.imshow('Test',self.img)

            self.pressedkey=cv2.waitKey(0)

            # Wait for ESC key to exit
            if self.pressedkey==27:
                cv2.destroyAllWindows()

    # Start of the main program here        
    if __name__=="__main__":
        LI=LoadImage()
        LI.loadImage()

Once the window displayed with the photo in it, I want to display on the console (terminal) the position of the mouse when I click over the picture. I have no idea how to perform this. Any help please?


Solution

  • Here is an example mouse callback function, that captures the left button double-click

    def draw_circle(event,x,y,flags,param):
        global mouseX,mouseY
        if event == cv2.EVENT_LBUTTONDBLCLK:
            cv2.circle(img,(x,y),100,(255,0,0),-1)
            mouseX,mouseY = x,y
    

    You then need to bind that function to a window that will capture the mouse click

    img = np.zeros((512,512,3), np.uint8)
    cv2.namedWindow('image')
    cv2.setMouseCallback('image',draw_circle)
    

    then, in a infinite processing loop (or whatever you want)

    while(1):
        cv2.imshow('image',img)
        k = cv2.waitKey(20) & 0xFF
        if k == 27:
            break
        elif k == ord('a'):
            print mouseX,mouseY
    

    What Does This Code Do?

    It stores the mouse position in global variables mouseX & mouseY every time you double click inside the black window and press the a key that will be created.

    elif k == ord('a'):
        print mouseX,mouseY
    

    will print the current stored mouse click location every time you press the a button.


    Code "Borrowed" from here.