45287b3541
overflow-hidden → overflow-y-auto so all nav items are reachable. Added /parent (Eltern-Portal) link with people icon. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
353 lines
14 KiB
Python
353 lines
14 KiB
Python
"""
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Row geometry detection for document layout analysis.
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Provides horizontal whitespace-gap analysis to detect text rows,
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word-center grid regularization, and fallback word-grouping.
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Extracted from cv_layout.py.
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Lizenz: Apache 2.0 (kommerziell nutzbar)
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DATENSCHUTZ: Alle Verarbeitung erfolgt lokal.
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"""
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import logging
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from typing import Dict, List
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import numpy as np
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try:
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import cv2
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except ImportError:
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cv2 = None # type: ignore[assignment]
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from cv_vocab_types import RowGeometry
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from cv_ocr_word_assembly import _group_words_into_lines
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from cv_layout_row_regularize import _regularize_row_grid
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logger = logging.getLogger(__name__)
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# =============================================================================
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# Row Geometry Detection (horizontal whitespace-gap analysis)
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# =============================================================================
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def detect_row_geometry(
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inv: np.ndarray,
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word_dicts: List[Dict],
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left_x: int, right_x: int,
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top_y: int, bottom_y: int,
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) -> List['RowGeometry']:
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"""Detect row geometry using horizontal whitespace-gap analysis.
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Algorithm overview (two phases):
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Phase 1 — Gap-based detection (Steps 1–6):
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1. Build a horizontal projection profile: for each y-pixel, sum the
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ink density across the content width. Only pixels within/near
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Tesseract word bounding boxes contribute (word_mask), so that
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images/illustrations don't merge adjacent text rows.
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2. Smooth the projection and find contiguous regions below a
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threshold (= gaps / horizontal whitespace between text lines).
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The threshold is 15% of the median non-zero density.
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3. Validate gaps against word bounding boxes — discard any gap
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that overlaps a word, or shift the gap boundary to avoid the word.
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4. Build rows from the spans between validated gaps.
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5. Detect header/footer rows: gaps in the top/bottom 15% of the
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page that are >= 2× the median gap size mark section boundaries.
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Phase 2 — Word-center regularization (_regularize_row_grid, Step 7):
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For each word, compute its vertical center (top + height/2).
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Group words into line clusters by Y-proximity (tolerance = 40% of
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the median gap-based row height).
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For each cluster, the line center = median of all word centers.
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The "pitch" = distance between consecutive line centers.
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Section breaks are detected where the pitch exceeds 1.8× the median.
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Within each section, row boundaries are placed at the midpoints
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between consecutive line centers:
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- Row top = midpoint to previous line center (or center - pitch/2 for first)
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- Row bottom = midpoint to next line center (or center + pitch/2 for last)
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This ensures rows tile without gaps or overlaps.
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Fallback:
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If < 2 gaps are found (very dense or uniform text), falls back to
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_build_rows_from_word_grouping() which groups words by Y proximity.
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Args:
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inv: Inverted binarized image (white text on black bg, full page).
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word_dicts: Word bounding boxes from Tesseract (relative to content ROI).
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left_x, right_x: Absolute X bounds of the content area.
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top_y, bottom_y: Absolute Y bounds of the content area.
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Returns:
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List of RowGeometry objects sorted top to bottom.
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"""
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content_w = right_x - left_x
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content_h = bottom_y - top_y
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if content_h < 10 or content_w < 10:
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logger.warning("detect_row_geometry: content area too small")
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return []
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# --- Step 1: Horizontal projection profile ---
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# For each y-pixel row, sum ink density across the content width.
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# A word-coverage mask ensures only pixels near Tesseract words contribute,
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# so that illustrations/images don't inflate the density and merge rows.
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content_strip = inv[top_y:bottom_y, left_x:right_x]
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WORD_PAD_Y = max(4, content_h // 300) # small vertical padding around words
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word_mask = np.zeros((content_h, content_w), dtype=np.uint8)
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for wd in word_dicts:
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y1 = max(0, wd['top'] - WORD_PAD_Y)
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y2 = min(content_h, wd['top'] + wd['height'] + WORD_PAD_Y)
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x1 = max(0, wd['left'])
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x2 = min(content_w, wd['left'] + wd['width'])
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word_mask[y1:y2, x1:x2] = 255
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masked_strip = cv2.bitwise_and(content_strip, word_mask)
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h_proj = np.sum(masked_strip, axis=1).astype(float)
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h_proj_norm = h_proj / (content_w * 255) if content_w > 0 else h_proj
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# --- Step 2: Smoothing + gap threshold ---
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# Smooth the projection to reduce noise, then threshold at 15% of the
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# median non-zero density. Pixels below this threshold are considered
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# "gap" (horizontal whitespace between text lines).
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# MIN_GAP_HEIGHT prevents tiny noise gaps from splitting rows.
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kernel_size = max(3, content_h // 200)
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if kernel_size % 2 == 0:
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kernel_size += 1
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h_smooth = np.convolve(h_proj_norm, np.ones(kernel_size) / kernel_size, mode='same')
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median_density = float(np.median(h_smooth[h_smooth > 0])) if np.any(h_smooth > 0) else 0.01
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gap_threshold = max(median_density * 0.15, 0.003)
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in_gap = h_smooth < gap_threshold
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MIN_GAP_HEIGHT = max(3, content_h // 500)
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# --- Step 3: Collect contiguous gap regions ---
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raw_gaps = [] # (start_y_rel, end_y_rel) relative to content ROI
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gap_start = None
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for y in range(len(in_gap)):
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if in_gap[y]:
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if gap_start is None:
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gap_start = y
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else:
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if gap_start is not None:
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gap_height = y - gap_start
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if gap_height >= MIN_GAP_HEIGHT:
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raw_gaps.append((gap_start, y))
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gap_start = None
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if gap_start is not None:
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gap_height = len(in_gap) - gap_start
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if gap_height >= MIN_GAP_HEIGHT:
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raw_gaps.append((gap_start, len(in_gap)))
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logger.info(f"RowGeometry: {len(raw_gaps)} raw gaps found (threshold={gap_threshold:.4f}, "
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f"min_height={MIN_GAP_HEIGHT}px)")
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# --- Step 4: Validate gaps against word bounding boxes ---
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# A gap is valid only if no word's bounding box overlaps it vertically.
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# If a word overlaps, try to shift the gap boundary above or below the
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# word. If neither shift yields enough room (>= MIN_GAP_HEIGHT), discard.
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validated_gaps = []
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for gap_start_rel, gap_end_rel in raw_gaps:
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overlapping = False
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for wd in word_dicts:
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word_top = wd['top']
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word_bottom = wd['top'] + wd['height']
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if word_top < gap_end_rel and word_bottom > gap_start_rel:
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overlapping = True
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break
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if not overlapping:
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validated_gaps.append((gap_start_rel, gap_end_rel))
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else:
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# Try to shift the gap to avoid overlapping words
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min_word_top = content_h
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max_word_bottom = 0
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for wd in word_dicts:
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word_top = wd['top']
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word_bottom = wd['top'] + wd['height']
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if word_top < gap_end_rel and word_bottom > gap_start_rel:
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min_word_top = min(min_word_top, word_top)
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max_word_bottom = max(max_word_bottom, word_bottom)
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if min_word_top - gap_start_rel >= MIN_GAP_HEIGHT:
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validated_gaps.append((gap_start_rel, min_word_top))
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elif gap_end_rel - max_word_bottom >= MIN_GAP_HEIGHT:
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validated_gaps.append((max_word_bottom, gap_end_rel))
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else:
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logger.debug(f"RowGeometry: gap [{gap_start_rel}..{gap_end_rel}] "
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f"discarded (word overlap, no room to shift)")
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logger.info(f"RowGeometry: {len(validated_gaps)} gaps after word validation")
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# --- Fallback if too few gaps ---
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if len(validated_gaps) < 2:
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logger.info("RowGeometry: < 2 gaps found, falling back to word grouping")
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return _build_rows_from_word_grouping(
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word_dicts, left_x, right_x, top_y, bottom_y, content_w, content_h,
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)
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validated_gaps.sort(key=lambda g: g[0])
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# --- Step 5: Header/footer detection via gap size ---
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HEADER_FOOTER_ZONE = 0.15
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GAP_MULTIPLIER = 2.0
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gap_sizes = [g[1] - g[0] for g in validated_gaps]
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median_gap = float(np.median(gap_sizes)) if gap_sizes else 0
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large_gap_threshold = median_gap * GAP_MULTIPLIER
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header_boundary_rel = None # y below which is header
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footer_boundary_rel = None # y above which is footer
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header_zone_limit = int(content_h * HEADER_FOOTER_ZONE)
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footer_zone_start = int(content_h * (1.0 - HEADER_FOOTER_ZONE))
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# Find largest gap in header zone
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best_header_gap = None
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for gs, ge in validated_gaps:
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gap_mid = (gs + ge) / 2
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gap_size = ge - gs
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if gap_mid < header_zone_limit and gap_size > large_gap_threshold:
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if best_header_gap is None or gap_size > (best_header_gap[1] - best_header_gap[0]):
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best_header_gap = (gs, ge)
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if best_header_gap is not None:
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header_boundary_rel = best_header_gap[1]
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logger.info(f"RowGeometry: header boundary at y_rel={header_boundary_rel} "
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f"(gap={best_header_gap[1] - best_header_gap[0]}px, "
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f"median_gap={median_gap:.0f}px)")
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# Find largest gap in footer zone
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best_footer_gap = None
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for gs, ge in validated_gaps:
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gap_mid = (gs + ge) / 2
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gap_size = ge - gs
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if gap_mid > footer_zone_start and gap_size > large_gap_threshold:
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if best_footer_gap is None or gap_size > (best_footer_gap[1] - best_footer_gap[0]):
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best_footer_gap = (gs, ge)
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if best_footer_gap is not None:
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footer_boundary_rel = best_footer_gap[0]
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logger.info(f"RowGeometry: footer boundary at y_rel={footer_boundary_rel} "
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f"(gap={best_footer_gap[1] - best_footer_gap[0]}px)")
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# --- Step 6: Build RowGeometry objects from gaps ---
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# Rows are the spans between consecutive gaps. The gap midpoints define
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# where one row ends and the next begins. Each row's height extends
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# from the end of the previous gap to the start of the next gap.
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row_boundaries = [] # (start_y_rel, end_y_rel)
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# Top of content to first gap
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if validated_gaps[0][0] > MIN_GAP_HEIGHT:
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row_boundaries.append((0, validated_gaps[0][0]))
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# Between gaps
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for i in range(len(validated_gaps) - 1):
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row_start = validated_gaps[i][1]
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row_end = validated_gaps[i + 1][0]
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if row_end - row_start > 0:
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row_boundaries.append((row_start, row_end))
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# Last gap to bottom of content
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if validated_gaps[-1][1] < content_h - MIN_GAP_HEIGHT:
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row_boundaries.append((validated_gaps[-1][1], content_h))
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rows = []
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for idx, (row_start_rel, row_end_rel) in enumerate(row_boundaries):
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# Determine row type
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row_mid = (row_start_rel + row_end_rel) / 2
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if header_boundary_rel is not None and row_mid < header_boundary_rel:
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row_type = 'header'
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elif footer_boundary_rel is not None and row_mid > footer_boundary_rel:
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row_type = 'footer'
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else:
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row_type = 'content'
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# Collect words in this row
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row_words = [w for w in word_dicts
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if w['top'] + w['height'] / 2 >= row_start_rel
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and w['top'] + w['height'] / 2 < row_end_rel]
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# Gap before this row
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gap_before = 0
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if idx == 0 and validated_gaps[0][0] > 0:
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gap_before = validated_gaps[0][0]
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elif idx > 0:
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# Find the gap just before this row boundary
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for gs, ge in validated_gaps:
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if ge == row_start_rel:
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gap_before = ge - gs
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break
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rows.append(RowGeometry(
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index=idx,
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x=left_x,
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y=top_y + row_start_rel,
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width=content_w,
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height=row_end_rel - row_start_rel,
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word_count=len(row_words),
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words=row_words,
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row_type=row_type,
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gap_before=gap_before,
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))
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# --- Step 7: Word-center grid regularization ---
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# Refine the gap-based rows using word vertical centers. For each word,
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# compute center_y = top + height/2. Group into line clusters, compute
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# the pitch (distance between consecutive line centers), and place row
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# boundaries at the midpoints between centers. This gives more precise
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# and evenly-spaced rows than the gap-based approach alone.
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# Also detects section breaks (headings, paragraphs) where the pitch
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# exceeds 1.8× the median, and handles each section independently.
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rows = _regularize_row_grid(rows, word_dicts, left_x, right_x, top_y,
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content_w, content_h, inv)
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type_counts = {}
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for r in rows:
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type_counts[r.row_type] = type_counts.get(r.row_type, 0) + 1
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logger.info(f"RowGeometry: {len(rows)} rows detected: {type_counts}")
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return rows
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def _build_rows_from_word_grouping(
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word_dicts: List[Dict],
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left_x: int, right_x: int,
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top_y: int, bottom_y: int,
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content_w: int, content_h: int,
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) -> List['RowGeometry']:
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"""Fallback: build rows by grouping words by Y position.
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Uses _group_words_into_lines() with a generous tolerance.
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No header/footer detection in fallback mode.
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"""
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if not word_dicts:
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return []
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y_tolerance = max(20, content_h // 100)
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lines = _group_words_into_lines(word_dicts, y_tolerance_px=y_tolerance)
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rows = []
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for idx, line_words in enumerate(lines):
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if not line_words:
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continue
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min_top = min(w['top'] for w in line_words)
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max_bottom = max(w['top'] + w['height'] for w in line_words)
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row_height = max_bottom - min_top
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rows.append(RowGeometry(
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index=idx,
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x=left_x,
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y=top_y + min_top,
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width=content_w,
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height=row_height,
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word_count=len(line_words),
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words=line_words,
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row_type='content',
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gap_before=0,
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))
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logger.info(f"RowGeometry (fallback): {len(rows)} rows from word grouping")
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return rows
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