separate characters from borders after thresholding

Question

I would like to separate characters from borders after thresholding the images:

Original image

Touching areas

Desired Output

I'm using python and OpenCV to do the thresholding. Thanks in advance for your help.

This is part of the code that makes the threshold

def threshold_image(img):
   gray_img = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

   resized_img = cv2.resize(gray_img
    , None
    , fx=5.0
    , fy=5.0
    , interpolation=cv2.INTER_CUBIC)

    resized_img = cv2.GaussianBlur(resized_img,(5,5),0)#(5,5)

   equalized_img = cv2.equalizeHist(resized_img)
   # height of the image
   alto = int(resized_img.shape[0])  # shape[0] = rows
   # width of the image 
   ancho = int(resized_img.shape[1])  # shape[1] = cols

   reduced = cv2.cvtColor(reduce_colors(cv2.cvtColor(equalized_img, cv2.COLOR_GRAY2BGR), 6), cv2.COLOR_BGR2GRAY)

   ret, mask = cv2.threshold(reduced, 110, 255, cv2.THRESH_BINARY)#64
   cv2.imwrite('licence_plate_mask.png', mask)

   return mask 

Answer 1

You can apply an erosion operation to your mask to disconnect the selected area.

You should be careful to not disconnect the "H" when eroding, you could change your kernel to affect the shape vertically the most.

You can read more about math morphology operators here.