tesseract for empty table cell

user_2067210 0
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I am using tesseract to convert image into text on CentOS instance, but I am not able to handle blank cells.

Output that I get from tesseract:

Legal entity Project Category Mon 08/ 20 Tue 08/ 21 Wed 08/ 22 Thu 08/23 Fri 08/24 Sat 08/25 Sun 08/ 26 Total

test Development Improvements - Improvem 8.00 8.00 8.00 8.00 8.00 40.00 H '9

Please note that in second line there is space after last 8 and before 40 (basically Sat/Sun cell are empty)

tesseract image-processing ocr
3 Answers

I would try to locate the region containing the text before performing the OCR part, making it my ROI. Then for the OCR part use the ROIs instead of the whole image. Then you can search if the ROI contains contours then it should perform OCR else make a blank space. Hope it helps a bit, cheers!

Example:

import cv2
import numpy as np

img = cv2.imread('table_so.png')

res = cv2.resize(img,None,fx=0.8, fy=0.8, interpolation = cv2.INTER_CUBIC)
h,w,ch = res.shape
cv2.rectangle(res, (0,0), (w,h), (0,0,0), 10)

gray = cv2.cvtColor(res, cv2.COLOR_BGR2GRAY)
_, thresh = cv2.threshold(gray,220,255,cv2.THRESH_BINARY)
_, contours, hierarchy = cv2.findContours(thresh,cv2.RETR_TREE,cv2.CHAIN_APPROX_NONE)
sort_cnts = sorted(contours, key=lambda ctr: cv2.boundingRect(ctr)[0] + cv2.boundingRect(ctr)[1] * res.shape[1] )

ROIs = []

for cnt in sort_cnts:
    x,y,w,h = cv2.boundingRect(cnt)
    if 2000 > w > 70 and h < 100:
        ROI = res[y:y+h, x:x+w]
        ROIs.append(ROI)
        cv2.rectangle(res, (x,y), (x+w,y+h), (0,255,0), 2)

for i in ROIs:
    roi = i
    gray = cv2.cvtColor(roi, cv2.COLOR_BGR2GRAY)
    _, thresh = cv2.threshold(gray,220,255,cv2.THRESH_BINARY)
    _, contours, hierarchy = cv2.findContours(thresh,cv2.RETR_TREE,cv2.CHAIN_APPROX_NONE)
    if len(contours) > 1:
        print('DO OCR HERE')
    else:
        print('BLANK SPACE')
    cv2.imshow('img', gray)
    cv2.waitKey(0)
    cv2.destroyAllWindows()

cv2.imshow('img', res)

Result:

enter image description here

(The green boxes are ROIs)

  • DO OCR HERE
  • DO OCR HERE
  • DO OCR HERE
  • DO OCR HERE
  • DO OCR HERE
  • DO OCR HERE
  • DO OCR HERE
  • DO OCR HERE
  • DO OCR HERE
  • BLANK SPACE
  • BLANK SPACE
  • BLANK SPACE
user_97897370

You can either train Tesseract and make it recognize blank spaces (not recommended, since it can mess up the 100% output you're getting), or resolve the issue by coding. Unfortunatelly, there's no way to just train Tesseract the way you want it to.

The best solution i see here is displaying a 0 or something alike (any character you feel comfortable with) at Saturday and Sunday, so that Tesseract can see them and you can react to that.

user_97404860
user_7540600
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