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Alex-GilbertandClaude Opus 4.6
043aae5abb
Add _score_font_line_pixel() which renders candidate text and compares pixels against the actual page image using Dice coefficient overlap. This captures glyph shape differences that the old word-width MAE approach cannot distinguish (e.g. serif vs sans-serif). Co-Authored-By: Claude Opus 4.6 <[email protected]>
111 lines
3.8 KiB
Python
111 lines
3.8 KiB
Python
"""Test pixel-based font scoring — render known text and verify detection."""
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import numpy as np
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from PIL import Image, ImageDraw, ImageFont
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from unredact.pipeline.font_detect import _find_font_path, _score_font_line_pixel
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from unredact.pipeline.ocr import OcrChar, OcrLine
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def _make_line_and_crop(font_name: str, font_size: int, text: str):
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"""Render text with a known font and return (OcrLine, grayscale_crop)."""
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font_path = _find_font_path(font_name)
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assert font_path is not None, f"Font {font_name} not found"
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font = ImageFont.truetype(str(font_path), font_size)
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# Measure the text
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bbox = font.getbbox(text)
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text_w = bbox[2] - bbox[0]
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text_h = bbox[3] - bbox[1]
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# Render onto a white canvas with some padding
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pad = 10
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img = Image.new("L", (text_w + pad * 2, text_h + pad * 2), 255)
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draw = ImageDraw.Draw(img)
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draw.text((pad - bbox[0], pad - bbox[1]), text, font=font, fill=0)
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# Build a fake OcrLine with word-level bounding boxes
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words = text.split()
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chars = []
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cursor_x = pad
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for wi, word in enumerate(words):
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word_bbox = font.getbbox(word)
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word_w = word_bbox[2] - word_bbox[0]
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char_w = word_w / len(word)
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for ci, ch in enumerate(word):
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chars.append(OcrChar(
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text=ch,
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x=int(cursor_x + ci * char_w),
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y=pad,
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w=max(1, int(char_w)),
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h=text_h,
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conf=95.0,
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))
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cursor_x += word_w
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# Add space between words
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if wi < len(words) - 1:
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space_w = font.getlength(" ")
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chars.append(OcrChar(
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text=" ", x=int(cursor_x), y=pad,
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w=max(1, int(space_w)), h=text_h, conf=95.0,
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))
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cursor_x += space_w
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line = OcrLine(
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chars=chars,
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x=pad, y=pad,
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w=int(cursor_x - pad), h=text_h,
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)
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crop = np.array(img)
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return line, crop
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def test_pixel_scoring_correct_font_scores_highest():
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"""The correct font+size should score higher than a wrong font."""
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text = "Got it. Sent an email."
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line, crop = _make_line_and_crop("Times New Roman", 50, text)
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tnr_path = _find_font_path("Times New Roman")
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arial_path = _find_font_path("Arial")
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assert tnr_path and arial_path
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tnr_font = ImageFont.truetype(str(tnr_path), 50)
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arial_font = ImageFont.truetype(str(arial_path), 50)
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arial_44_font = ImageFont.truetype(str(arial_path), 44)
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score_tnr = _score_font_line_pixel(tnr_font, line, crop)
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score_arial = _score_font_line_pixel(arial_font, line, crop)
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score_arial_44 = _score_font_line_pixel(arial_44_font, line, crop)
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# TNR at correct size should beat Arial at any size
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assert score_tnr > score_arial, (
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f"TNR@50 ({score_tnr:.3f}) should beat Arial@50 ({score_arial:.3f})"
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)
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assert score_tnr > score_arial_44, (
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f"TNR@50 ({score_tnr:.3f}) should beat Arial@44 ({score_arial_44:.3f})"
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)
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def test_pixel_scoring_wrong_size_scores_lower():
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"""The correct font at the wrong size should score lower."""
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text = "Got it. Sent an email."
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line, crop = _make_line_and_crop("Times New Roman", 50, text)
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tnr_path = _find_font_path("Times New Roman")
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assert tnr_path
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font_50 = ImageFont.truetype(str(tnr_path), 50)
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font_44 = ImageFont.truetype(str(tnr_path), 44)
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font_60 = ImageFont.truetype(str(tnr_path), 60)
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score_50 = _score_font_line_pixel(font_50, line, crop)
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score_44 = _score_font_line_pixel(font_44, line, crop)
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score_60 = _score_font_line_pixel(font_60, line, crop)
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assert score_50 > score_44, (
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f"TNR@50 ({score_50:.3f}) should beat TNR@44 ({score_44:.3f})"
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)
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assert score_50 > score_60, (
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f"TNR@50 ({score_50:.3f}) should beat TNR@60 ({score_60:.3f})"
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)
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