tesseract not able to read all digits accurately - opencv

Question

I'm using Tesseract to recognize numbers from images of a screen taken with a phone camera. I've done some preprocessing of the image: processed image, and using Tesseract, I'm able to get some mixed results. Using the following code on the above images, I get the following output: "EOE". However, with this image, processed image, I get an exact match: "39:45.8"
import cv2
import pytesseract
from PIL import Image, ImageEnhance
from matplotlib import pyplot as plt
orig_name = "time3.jpg";
image_name = "time3_.jpg";
img = cv2.imread(orig_name, 0)
img = cv2.medianBlur(img, 5)
img_th = cv2.adaptiveThreshold(img, 255,\
cv2.ADAPTIVE_THRESH_MEAN_C,cv2.THRESH_BINARY, 11, 2)
cv2.imshow('image', img_th)
cv2.waitKey(0)
cv2.imwrite(image_name, img_th)
im = Image.open(image_name)
time = pytesseract.image_to_string(im, config = "-psm 7")
print(time)
Is there anything I can do to get more consistent results?

Answer 1

I did three additional things to get it correct for the first Image.
You can set a whitelist for Tesseract. In your case we know that
there will only charachters from this List 01234567890.:. This
improves the accuracy significantly.
I resized the image to make it easier for tesseract.
I switched from psm mode 7 to 11 (Recoginze as much as possible)
Code:
import cv2
import pytesseract
from PIL import Image, ImageEnhance
orig_name = "./time1.jpg";
img = cv2.imread(orig_name)
height, width, channels = img.shape
imgResized = cv2.resize(img, ( width*3, height*3))
cv2.imshow("img",imgResized)
cv2.waitKey()
im = Image.fromarray(imgResized)
time = pytesseract.image_to_string(im, config ='--tessdata-dir "/home/rvq/github/tesseract/tessdata/" -c tessedit_char_whitelist=01234567890.: -psm 11 -oem 0')
print(time)
Note:
You can use Image.fromarray(imgResized) to convert an opencv image to a PIL Image. You don't have to write to disk and read it again.