How to extract decimal in image with Pytesseract

by PankajKushwaha   Last Updated August 13, 2019 20:26 PM - source

Image to Extract

Above is the image ,I have tried everything I could get from SO or google ,nothing seems to work. I can not get the exact value in image , I should get 2.10 , Instead it always get 210.

And it is not limited to this image only any image which have a decimal before number 1 tesseract ignores the decimal value.

 def returnAllowedAmount(self,imgpath):
        th = 127
        max_val = 255
        img = cv2.imread(imgpath,0) #Load Image in Memory
        img = cv2.resize(img, None, fx=2.5, fy=2.5, interpolation=cv2.INTER_CUBIC) #rescale Image
        img = cv2.medianBlur(img, 1)
        ret , img = cv2.threshold(img,th,max_val,cv2.THRESH_TOZERO)
        self.showImage(img)

        returnData = pytesseract.image_to_string(img,lang='eng',config='-psm 13 ' )
        returnData = ''.join(p for p in returnData if p.isnumeric() or p == ".") # REMOVE $ SIGN


Answers 1


Before throwing the image into Pytesseract, some preprocessing to clean/smooth the image helps. Here's a simple approach

  • Convert image to grayscale and enlarge image
  • Threshold
  • Perform morphological operations to clean image
  • Invert image

First we convert the image to grayscale, resize using the imutils library then threshold to obtain a binary image

enter image description here

Now we perform morphological transformations to smooth the image

enter image description here

Now we invert the image for Pytesseract and add a Gaussian blur

enter image description here

We use the --psm 10 config flag since we want to treat the image as a single character. Here's some additional configuration flags that could be useful

Results

$2.10

After filtering

2.10

import cv2
import pytesseract
import imutils

pytesseract.pytesseract.tesseract_cmd = r"C:\Program Files\Tesseract-OCR\tesseract.exe"

image = cv2.imread('1.png',0)
image = imutils.resize(image, width=300)
thresh = cv2.threshold(image, 150, 255, cv2.THRESH_BINARY_INV)[1]

kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (3,3))
opening = cv2.morphologyEx(thresh, cv2.MORPH_CLOSE, kernel)

result = 255 - opening 
result = cv2.GaussianBlur(result, (5,5), 0)

data = pytesseract.image_to_string(result, lang='eng',config='--psm 10 ')
processed_data = ''.join(char for char in data if char.isnumeric() or char == '.')
print(data)
print(processed_data)

cv2.imshow('thresh', thresh)
cv2.imshow('opening', opening)
cv2.imshow('result', result)
cv2.waitKey()
nathancy
nathancy
August 13, 2019 20:25 PM

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