Coverage for image_processing/text_cleaner.py : 80%

""" 

---------------------------------------------------------------------- 

Authors: Jan-Justin van Tonder 

---------------------------------------------------------------------- 

This file contains the logic used to manage the removal of characters 

from an input string. 

---------------------------------------------------------------------- 

""" 

import re 

from hutts_utils.hutts_logger import logger 

class TextCleaner: 

""" 

This class is encapsulates the logic required to clean the OCR output string produced from an image of an ID. 

Attributes: 

_deplorables (list): A list of strings that contain characters that is to be filtered out from the OCR output 

string during string cleaning. 

""" 

def __init__(self): 

""" 

Responsible for initialising the TextCleaner object. 

""" 

# Logging for debugging purposes. 

logger.debug('Initialising %s...' % type(self).__name__) 

# Specify initial list of undesirable characters. 

self._deplorables = ['_'] 

def clean_up(self, in_string, deplorables=None): 

""" 

This function serves to receive an input string, clean it up through removing undesirable characters and 

unnecessary whitespace, and to return the cleaned string. 

Authors: 

Jan-Justin van Tonder 

Args: 

in_string (str): The input string that is to be cleaned. 

deplorables (list, Optional): A list of characters that are to be filtered from the input string. 

Returns: 

str: A string that has been stripped of undesirable characters and unnecessary whitespace. 

Raises: 

TypeError: If in_string is not a string. 

TypeError: If deplorables is not a list of strings. 

""" 

# Check if the correct argument types have been passed in. 

if not isinstance(in_string, str): 

raise TypeError( 

'Bad type for arg in_string - expected string. Received type "%s".' % 

type(in_string).__name__ 

) 

if deplorables and (not isinstance(deplorables, list) or not isinstance(deplorables[0], str)): 

raise TypeError( 

'Bad type for arg deplorables - expected list of strings. Received type "%s".' % 

type(deplorables).__name__ 

) 

# Remove undesirable characters, spaces and newlines. 

compiled_deplorable_re = self._compile_deplorables(deplorables) 

sanitised = re.sub(compiled_deplorable_re, '', in_string) 

# Remove empty lines in-between text-filled lines. 

stripped_and_sanitised = re.sub(r'(\n\s*\n)', '\n', sanitised) 

# Remove multiple spaces before and after text-filled line. 

clean_text = re.sub(r'(\s*\n\s*)', '\n', stripped_and_sanitised) 

# Remove multiple spaces in-between text-filled line. 

clean_text = re.sub(r'( +)', ' ', clean_text) 

# Lastly, strip the trailing and leading spaces. 

clean_text = clean_text.strip() 

# Return cleaned text. 

return clean_text 

def _compile_deplorables(self, deplorables): 

""" 

This function is responsible for compiling a regex pattern that is used to filter out the characters that 

were deemed undesirable from a string. 

Authors: 

Jan-Justin van Tonder 

Args: 

deplorables (list): A list of characters that are to be filtered from the input string. 

Returns: 

A compiled regex pattern used to match undesirable characters in a string. 

""" 

# Append to existing list of undesirable characters if there is a given list of 

# undesirable characters 

if deplorables is not None: 

# Escape and append the list of undesirable characters. 

self._deplorables += re.escape(''.join(deplorables)) 

# Define a class of characters that we wish to keep for the regex 

# that is to be compiled. 

reg_exp = r'[^\w\d\s-]' 

# If the existing list of undesirable characters is not empty, 

# add the list of undesirable characters to the regex that is to be compiled. 

reg_exp += r'|[' + ''.join(self._deplorables) + ']' 

# Returned a compiled regular expression pattern to use for matching. 

return re.compile(reg_exp, re.UNICODE)