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Fix some special cases
This commit is contained in:
Benjamin Rosemann
parent
d7a74fa58b
commit
5277593bdb
2 changed files with 83 additions and 40 deletions
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@ -117,6 +117,7 @@ def match_longest_gt_lines(gt_lines: List["Part"],
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if best_match and best_gt:
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splitted = remove_or_split(best_gt, best_match.gt, gt_lines)
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if splitted:
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# according to the paper the match is not put back, we deviate...
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gt_lines.append(best_match.gt)
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best_match = None
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if best_match and best_ocr:
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@ -134,13 +135,12 @@ def match_gt_line(gt_line: "Part",
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Reference: contains steps 3 of the flexible character accuracy algorithm.
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TODO: Make penalty function configurable?
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TODO: Add empty ocr line to avoid having nonesense one character alignments?
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:return: Match object and the matched ocr line.
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"""
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min_penalty = float('inf')
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best_match, best_ocr = None, None
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for ocr_line in ocr_lines:
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for ocr_line in [*ocr_lines]:
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match = match_lines(gt_line, ocr_line)
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penalty = calculate_penalty(gt_line, ocr_line, match, coef)
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if penalty < min_penalty:
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@ -177,20 +177,42 @@ def match_lines(gt_line: "Part", ocr_line: "Part") -> Optional["Match"]:
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Reference: see figure 2 in the paper.
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TODO: make distance function configurable?
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TODO: rethink @lru_cache
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:return: Match object if one is found.
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"""
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min_length = min(gt_line.length, ocr_line.length)
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best_match = None
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best_i, best_j = 0, 0
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if min_length == 0:
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return best_match
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length_diff = gt_line.length - ocr_line.length
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min_edit_dist = float('inf')
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# TODO: handle deletes and replacements by extending the length.
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for i in range(0, max(1, length_diff + 1)):
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for j in range(0, max(1, -1 * length_diff + 1)):
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match = distance(gt_line.substring(rel_start=i, rel_end=i + min_length),
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ocr_line.substring(rel_start=j, rel_end=j + min_length))
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gt_parts = [(i, gt_line.substring(rel_start=i, rel_end=i + min_length))
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for i in range(0, max(1, length_diff + 1))]
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ocr_parts = [(j, ocr_line.substring(rel_start=j, rel_end=j + min_length))
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for j in range(0, max(1, -1 * length_diff + 1))]
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# add full line and empty line match
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gt_parts = [*gt_parts, (0, gt_line), (0, gt_line)]
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ocr_parts = [*ocr_parts, (0, ocr_line),
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(0, Part(text="", line=gt_line.line, start=gt_line.start))]
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for i, gt_part in gt_parts:
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for j, ocr_part in ocr_parts:
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match = distance(gt_part, ocr_part)
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edit_dist = score_edit_distance(match)
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if edit_dist < min_edit_dist:
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min_edit_dist = edit_dist
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best_match = match
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best_i, best_j = i, j
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if best_match and (best_match.dist.delete or best_match.dist.replace):
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part_length = best_match.gt.length
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additional_length = best_match.dist.delete + best_match.dist.replace
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for k in range(part_length + 1, part_length + additional_length + 1):
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match = distance(gt_line.substring(rel_start=best_i, rel_end=best_i + k),
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ocr_line.substring(rel_start=best_j, rel_end=best_j + k))
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edit_dist = score_edit_distance(match)
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if edit_dist < min_edit_dist:
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min_edit_dist = edit_dist
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@ -205,6 +227,7 @@ def distance(gt: "Part", ocr: "Part") -> "Match":
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Using the already available `editops()` function with the Levenshtein distance.
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TODO: replace with @cache annotation in Python 3.9
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TODO: rethink @lru_cache
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:return: Match object containing the lines and the editing operations.
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"""
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@ -33,6 +33,7 @@ COMPLEX_CASES = [
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]
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EXTENDED_CASES = [
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# See figure 4 in 10.1016/j.patrec.2020.02.003
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# A: No errors
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((0, 1, 2, 3, 4, 11, 5, 6, 7, 8, 9),
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(0, 1, 2, 3, 4, 11, 5, 6, 7, 8, 9),
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@ -70,14 +71,18 @@ EXTENDED_CASES = [
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EDIT_ARGS = "gt,ocr,expected_dist"
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SIMPLE_EDITS = [
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(Part(text="a").substring(), Part(text="a"), Distance(match=1)),
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(Part(text="a").substring(), Part(text="b"), Distance(replace=1)),
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(Part(text="abcd").substring(), Part(text="beed"),
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(Part(text="a"), Part(text="a"), Distance(match=1)),
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(Part(text="aaa"), Part(text="aaa"), Distance(match=3)),
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(Part(text="abcd"), Part(text="beed"),
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Distance(match=2, replace=1, insert=1, delete=1)),
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]
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def extended_case_to_text(gt, ocr):
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"""Generate sentence from reading order encoding.
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See figure 4 in 10.1016/j.patrec.2020.02.003
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"""
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sentence = ("Eight", "happy", "frogs", "scuba", "dived",
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"Jenny", "chick", "flaps", "white", "wings",
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"", "\n")
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@ -93,38 +98,45 @@ def test_flexible_character_accuracy_simple(gt, ocr, first_line_score, all_line_
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assert score == pytest.approx(all_line_score)
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@pytest.mark.xfail
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@pytest.mark.parametrize("ocr", [
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"1 hav\nnospecial\ntalents.\nI am one\npassionate\ncuriousity.\"\nAlberto\nEmstein",
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"1 hav\nnospecial\ntalents. Alberto\nI am one Emstein\npassionate\ncuriousity.\"",
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"Alberto\nEmstein\n1 hav\nnospecial\ntalents.\nI am one\npassionate\ncuriousity.\""
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@pytest.mark.parametrize("config,ocr", [
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("Config I",
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"1 hav\nnospecial\ntalents.\nI am one\npassionate\ncuriousity.\"\nAlberto\nEmstein"
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),
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("Config II",
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"1 hav\nnospecial\ntalents. Alberto\nI am one Emstein\npassionate\ncuriousity.\""
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),
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("Config III",
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"Alberto\nEmstein\n1 hav\nnospecial\ntalents.\nI am one\npassionate\ncuriousity.\""
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),
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])
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def test_flexible_character_accuracy(ocr):
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"""Tests from figure 3 in the paper.
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TODO: We have a 2 percent deviation from the original because of redistributed
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one character alignments (e.g. the y-insert replaces the y-delete).
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"""
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gt = """"I have
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no special
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talent.
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I am only
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passionately
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curious."
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Albert
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Einstein
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"""
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replacements = 3
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inserts = 5
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deletes = 7
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def test_flexible_character_accuracy(config, ocr):
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"""Tests from figure 3 in the paper."""
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gt = "\"I have\nno special\ntalent." \
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"\nI am only\npassionately\ncurious.\"" \
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"\nAlbert\nEinstein"
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replacements, inserts, deletes = 3, 5, 7
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chars = len(gt) - gt.count("\n")
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assert replacements + inserts + deletes == 15
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edits = Distance(match=chars - deletes - replacements, replace=replacements,
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insert=inserts, delete=deletes)
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expected = character_accuracy(edits)
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assert expected == pytest.approx(0.779, abs=0.0005)
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assert chars == 68
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# We consider whitespace as error and in Config II two additional
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# whitespaces have been introduced. One will be counted as insert.
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# The other whitespace will be counted as replacement,
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# additionally reducing the number of deletes.
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if config == "Config II":
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inserts += 1
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replacements += 1
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deletes -= 1
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expected_dist = Distance(match=chars - deletes - replacements, replace=replacements,
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insert=inserts, delete=deletes)
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expected_score = character_accuracy(expected_dist)
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result, matches = flexible_character_accuracy(gt, ocr)
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assert result == pytest.approx(expected, abs=0.0005)
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agg = reduce(lambda acc, match: acc + Counter(match.dist._asdict()),
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matches, Counter())
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dist = Distance(**agg)
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assert dist == expected_dist
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assert result == pytest.approx(expected_score, abs=0.0005)
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@pytest.mark.parametrize(CASE_ARGS, EXTENDED_CASES)
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@ -191,9 +203,15 @@ def test_remove_or_split(original, match, expected_lines):
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@pytest.mark.parametrize(EDIT_ARGS, [
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*SIMPLE_EDITS,
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(Part(text="a"), Part(text="b"), Distance(delete=1)),
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(Part(text="aaa"), Part(text="bbb"), Distance(delete=3)),
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(Part(text="aaabbbaaa"), Part(text="bbb"), Distance(match=3)),
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(Part(text="bbb"), Part(text="aaabbbaaa"), Distance(match=3)),
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(Part(text=""), Part(text=""), None)
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(Part(text=""), Part(text=""), None),
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(Part(text="abcd"), Part(text="acd"), Distance(match=3, delete=1)),
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(Part(text="abc"), Part(text="abdc"), Distance(match=3, insert=1)),
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(Part(text="aaabbbaaaddd"), Part(text="aaabcbaaa"), Distance(match=8, replace=1)),
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(Part(text="aaabbbccc"), Part(text="aaabbbdddccc"), Distance(match=9, insert=3)),
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])
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def test_match_lines(gt, ocr, expected_dist):
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match = match_lines(gt, ocr)
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@ -210,6 +228,8 @@ def test_match_lines(gt, ocr, expected_dist):
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(Part(text="").substring(), Part(text=""), Distance()),
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(Part(text="ab").substring(), Part("a"), Distance(match=1, delete=1)),
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(Part(text="a").substring(), Part("ab"), Distance(match=1, insert=1)),
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(Part(text="a"), Part(text="b"), Distance(replace=1)),
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(Part(text="aaa"), Part(text="bbb"), Distance(replace=3)),
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])
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def test_distance(gt, ocr, expected_dist):
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match = distance(gt, ocr)
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