在 OpenCV 中裁剪垂直计数，获取边界框边框而不是区域

Question

I am trying to extract columns of a table in an image using opencv . I have managed to successfully identify the vertical regions of interest as shown in the image below:

My problem is when I am trying to extract and save those regions of interest I am getting a 6 vertical lines of the border of the bounding rectangle as opposed to the region in between them.

This is the code I am using to achieve this:

import cv2
import numpy as np

image = cv2.imread('x.png')
gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
blur = cv2.GaussianBlur(gray, (3,3), 0)
thresh = cv2.threshold(blur, 0, 255, cv2.THRESH_BINARY_INV + cv2.THRESH_OTSU)[1]

vertical_kernel = cv2.getStructuringElement(cv2.MORPH_RECT, (1,50))
vertical_mask = cv2.morphologyEx(thresh, cv2.MORPH_OPEN, vertical_kernel, iterations=1)
 
cnts = cv2.findContours(vertical_mask, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)[0]
for c in cnts:
    cv2.drawContours(image, [c], -1, (36,255,12), -1)

idx = 0
for c in cnts:
    x,y,w,h = cv2.boundingRect(c)

    idx+=1
    new_img=image[y:y+h,x:x+w]
    cv2.imwrite(str(idx) + '.png', new_img)

cv2.imshow("im.png",image)
cv2.waitKey(0)
cv2.destroyAllWindows()

Any ideas as to how I can solve this problem? Edit: This 2 is is the image of the right most border, as you can see there is some text

Answer 1

The bounding boxes you are drawing are from each line, not from the columns. What you should do is take the two points from some line, take the other two points from the line next to it, and using this 4 points you have defined the rectangle which is your column.

All this, of course assuming they are sorted from left to right, by coordinates. But opencv doesn't guarantee us they are sorted that way. So sort them first, and then draw rectangles over consecutive two lines