How to process and extract text from image

Question

I'm trying to extract text from image using python cv2. The result is pathetic and I can't figure out a way to improve my code. I believe the image needs to be processed before the extraction of text but not sure how.

Sample image

I've tried to convert it into black and white but no luck.

import cv2
import os
import pytesseract
from PIL import Image
import time

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

cam = cv2.VideoCapture(1,cv2.CAP_DSHOW)

cam.set(cv2.CAP_PROP_FRAME_WIDTH, 8000)
cam.set(cv2.CAP_PROP_FRAME_HEIGHT, 6000)

while True:
    return_value,image = cam.read()
    image=cv2.cvtColor(image,cv2.COLOR_BGR2GRAY)
    image = image[127:219, 508:722]
    #(thresh, image) = cv2.threshold(image, 128, 255, cv2.THRESH_BINARY | cv2.THRESH_OTSU)
    cv2.imwrite('test.jpg',image)
    print('Text detected: {}'.format(pytesseract.image_to_string(Image.open('test.jpg'))))
    time.sleep(2)

cam.release()
#os.system('del test.jpg')

You could also try to use EasyOCR. In my case the results were much better compared to Tesseract where it was just random text. At the moment, a custom model using EasyOCR cannot be trained. — Rishik Mani

nathancy nathancy · Accepted Answer · 2019-08-28T21:54:34

Preprocessing to clean the image before performing text extraction can help. Here's a simple approach

Convert image to grayscale and sharpen image
Adaptive threshold
Perform morpholgical operations to clean image
Invert image

First we convert to grayscale then sharpen the image using a sharpening kernel

Next we adaptive threshold to obtain a binary image

Now we perform morphological transformations to smooth the image

Finally we invert the image

import cv2
import numpy as np

image = cv2.imread('1.jpg')
gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
sharpen_kernel = np.array([[-1,-1,-1], [-1,9,-1], [-1,-1,-1]])
sharpen = cv2.filter2D(gray, -1, sharpen_kernel)
thresh = cv2.threshold(sharpen, 0, 255, cv2.THRESH_BINARY_INV + cv2.THRESH_OTSU)[1]

kernel = cv2.getStructuringElement(cv2.MORPH_RECT, (3,3))
close = cv2.morphologyEx(thresh, cv2.MORPH_CLOSE, kernel, iterations=1)
result = 255 - close

cv2.imshow('sharpen', sharpen)
cv2.imshow('thresh', thresh)
cv2.imshow('close', close)
cv2.imshow('result', result)
cv2.waitKey()

How to process and extract text from image

1 Answers