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dinglehopper/qurator/dinglehopper/character_error_rate.py

45 lines
1.1 KiB
Python

from __future__ import division
import unicodedata
from typing import Tuple
from multimethod import multimethod
from uniseg.graphemecluster import grapheme_clusters
from qurator.dinglehopper.edit_distance import distance
from qurator.dinglehopper.ocr_files import ExtractedText
@multimethod
def character_error_rate_n(reference: str, compared: str) -> Tuple[float, int]:
"""
Compute character error rate.
:return: character error rate and length of the reference
"""
d = distance(reference, compared)
n = len(list(grapheme_clusters(unicodedata.normalize('NFC', reference))))
if d == 0:
return 0, n
if n == 0:
return float('inf'), n
return d/n, n
# XXX Should we really count newlines here?
@multimethod
def character_error_rate_n(reference: ExtractedText, compared: ExtractedText) -> Tuple[float, int]:
return character_error_rate_n(reference.text, compared.text)
def character_error_rate(reference, compared) -> float:
"""
Compute character error rate.
:return: character error rate
"""
cer, _ = character_error_rate_n(reference, compared)
return cer