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breakpilot-lehrer/klausur-service/backend/cv_box_layout.py
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Bullet indentation detection: group continuation lines into bullets
Flowing/bullet_list layout now analyzes left-edge indentation:
- Lines at minimum indent = bullet start / main level
- Lines indented >15px more = continuation (belongs to previous bullet)
- Continuation lines merged with \n into parent bullet cell
- Missing bullet markers (•) auto-added when pattern is clear

Example: 7 OCR lines → 3 items (1 header + 2 bullets × 3 lines each)
"German leihen" header, then two bullet groups with indented examples.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-04-13 16:57:16 +02:00

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"""
Box layout classifier — detects internal layout type of embedded boxes.
Classifies each box as: flowing | columnar | bullet_list | header_only
and provides layout-appropriate grid building.
Used by the Box-Grid-Review step to rebuild box zones with correct structure.
"""
import logging
import re
import statistics
from typing import Any, Dict, List, Optional, Tuple
logger = logging.getLogger(__name__)
# Bullet / list-item patterns at the start of a line
_BULLET_RE = re.compile(
r'^[\-\u2022\u2013\u2014\u25CF\u25CB\u25AA\u25A0•·]\s' # dash, bullet chars
r'|^\d{1,2}[.)]\s' # numbered: "1) " or "1. "
r'|^[a-z][.)]\s' # lettered: "a) " or "a. "
)
def classify_box_layout(
words: List[Dict],
box_w: int,
box_h: int,
) -> str:
"""Classify the internal layout of a detected box.
Args:
words: OCR word dicts within the box (with top, left, width, height, text)
box_w: Box width in pixels
box_h: Box height in pixels
Returns:
'header_only' | 'bullet_list' | 'columnar' | 'flowing'
"""
if not words:
return "header_only"
# Group words into lines by y-proximity
lines = _group_into_lines(words)
# Header only: very few words or single line
total_words = sum(len(line) for line in lines)
if total_words <= 5 or len(lines) <= 1:
return "header_only"
# Bullet list: check if majority of lines start with bullet patterns
bullet_count = 0
for line in lines:
first_text = line[0].get("text", "") if line else ""
if _BULLET_RE.match(first_text):
bullet_count += 1
# Also check if first word IS a bullet char
elif first_text.strip() in ("-", "", "", "", "·", "", ""):
bullet_count += 1
if bullet_count >= len(lines) * 0.4 and bullet_count >= 2:
return "bullet_list"
# Columnar: check for multiple distinct x-clusters
if len(lines) >= 3 and _has_column_structure(words, box_w):
return "columnar"
# Default: flowing text
return "flowing"
def _group_into_lines(words: List[Dict]) -> List[List[Dict]]:
"""Group words into lines by y-proximity."""
if not words:
return []
sorted_words = sorted(words, key=lambda w: (w["top"], w["left"]))
heights = [w["height"] for w in sorted_words if w.get("height", 0) > 0]
median_h = statistics.median(heights) if heights else 20
y_tolerance = max(median_h * 0.5, 5)
lines: List[List[Dict]] = []
current_line: List[Dict] = [sorted_words[0]]
current_y = sorted_words[0]["top"]
for w in sorted_words[1:]:
if abs(w["top"] - current_y) <= y_tolerance:
current_line.append(w)
else:
lines.append(sorted(current_line, key=lambda ww: ww["left"]))
current_line = [w]
current_y = w["top"]
if current_line:
lines.append(sorted(current_line, key=lambda ww: ww["left"]))
return lines
def _has_column_structure(words: List[Dict], box_w: int) -> bool:
"""Check if words have multiple distinct left-edge clusters (columns)."""
if box_w <= 0:
return False
lines = _group_into_lines(words)
if len(lines) < 3:
return False
# Collect left-edges of non-first words in each line
# (first word of each line often aligns regardless of columns)
left_edges = []
for line in lines:
for w in line[1:]: # skip first word
left_edges.append(w["left"])
if len(left_edges) < 4:
return False
# Check if left edges cluster into 2+ distinct groups
left_edges.sort()
gaps = [left_edges[i + 1] - left_edges[i] for i in range(len(left_edges) - 1)]
if not gaps:
return False
median_gap = statistics.median(gaps)
# A column gap is typically > 15% of box width
column_gap_threshold = box_w * 0.15
large_gaps = [g for g in gaps if g > column_gap_threshold]
return len(large_gaps) >= 1
def build_box_zone_grid(
zone_words: List[Dict],
box_x: int,
box_y: int,
box_w: int,
box_h: int,
zone_index: int,
img_w: int,
img_h: int,
layout_type: Optional[str] = None,
) -> Dict[str, Any]:
"""Build a grid for a box zone with layout-aware processing.
If layout_type is None, auto-detects it.
For 'flowing' and 'bullet_list', forces single-column layout.
For 'columnar', uses the standard multi-column detection.
For 'header_only', creates a single cell.
Returns the same format as _build_zone_grid (columns, rows, cells, header_rows).
"""
from grid_editor_helpers import _build_zone_grid, _cluster_rows
if not zone_words:
return {
"columns": [],
"rows": [],
"cells": [],
"header_rows": [],
"box_layout_type": layout_type or "header_only",
"box_grid_reviewed": False,
}
# Auto-detect layout if not specified
if not layout_type:
layout_type = classify_box_layout(zone_words, box_w, box_h)
logger.info(
"Box zone %d: layout_type=%s, %d words, %dx%d",
zone_index, layout_type, len(zone_words), box_w, box_h,
)
if layout_type == "header_only":
# Single cell with all text concatenated
all_text = " ".join(
w.get("text", "") for w in sorted(zone_words, key=lambda ww: (ww["top"], ww["left"]))
).strip()
return {
"columns": [{"col_index": 0, "index": 0, "label": "column_text", "col_type": "column_1",
"x_min_px": box_x, "x_max_px": box_x + box_w,
"x_min_pct": round(box_x / img_w * 100, 2) if img_w else 0,
"x_max_pct": round((box_x + box_w) / img_w * 100, 2) if img_w else 0,
"bold": False}],
"rows": [{"index": 0, "row_index": 0,
"y_min": box_y, "y_max": box_y + box_h, "y_center": box_y + box_h / 2,
"y_min_px": box_y, "y_max_px": box_y + box_h,
"y_min_pct": round(box_y / img_h * 100, 2) if img_h else 0,
"y_max_pct": round((box_y + box_h) / img_h * 100, 2) if img_h else 0,
"is_header": True}],
"cells": [{
"cell_id": f"Z{zone_index}_R0C0",
"row_index": 0,
"col_index": 0,
"col_type": "column_1",
"text": all_text,
"word_boxes": zone_words,
}],
"header_rows": [0],
"box_layout_type": layout_type,
"box_grid_reviewed": False,
}
if layout_type in ("flowing", "bullet_list"):
# Force single column — each line becomes one row with one cell.
# Detect bullet structure from indentation and merge continuation
# lines into the bullet they belong to.
lines = _group_into_lines(zone_words)
column = {
"col_index": 0, "index": 0, "label": "column_text", "col_type": "column_1",
"x_min_px": box_x, "x_max_px": box_x + box_w,
"x_min_pct": round(box_x / img_w * 100, 2) if img_w else 0,
"x_max_pct": round((box_x + box_w) / img_w * 100, 2) if img_w else 0,
"bold": False,
}
# --- Detect indentation levels ---
line_indents = []
for line_words in lines:
if not line_words:
line_indents.append(0)
continue
min_left = min(w["left"] for w in line_words)
line_indents.append(min_left - box_x)
# Find the minimum indent (= bullet/main level)
valid_indents = [ind for ind in line_indents if ind >= 0]
min_indent = min(valid_indents) if valid_indents else 0
# Indentation threshold: lines indented > 15px more than minimum
# are continuation lines belonging to the previous bullet
INDENT_THRESHOLD = 15
# --- Group lines into logical items (bullet + continuations) ---
# Each item is a list of line indices
items: List[List[int]] = []
for li, indent in enumerate(line_indents):
is_continuation = (indent > min_indent + INDENT_THRESHOLD) and len(items) > 0
if is_continuation:
items[-1].append(li)
else:
items.append([li])
logger.info(
"Box zone %d flowing: %d lines → %d items (indents=%s, min=%d, threshold=%d)",
zone_index, len(lines), len(items),
[int(i) for i in line_indents], int(min_indent), INDENT_THRESHOLD,
)
# --- Build rows and cells from grouped items ---
rows = []
cells = []
header_rows = []
for row_idx, item_line_indices in enumerate(items):
# Collect all words from all lines in this item
item_words = []
item_texts = []
for li in item_line_indices:
if li < len(lines):
item_words.extend(lines[li])
line_text = " ".join(w.get("text", "") for w in lines[li]).strip()
if line_text:
item_texts.append(line_text)
if not item_words:
continue
y_min = min(w["top"] for w in item_words)
y_max = max(w["top"] + w["height"] for w in item_words)
y_center = (y_min + y_max) / 2
row = {
"index": row_idx,
"row_index": row_idx,
"y_min": y_min,
"y_max": y_max,
"y_center": y_center,
"y_min_px": y_min,
"y_max_px": y_max,
"y_min_pct": round(y_min / img_h * 100, 2) if img_h else 0,
"y_max_pct": round(y_max / img_h * 100, 2) if img_h else 0,
"is_header": False,
}
rows.append(row)
# Join multi-line text with newline for display
merged_text = "\n".join(item_texts)
# Add bullet marker if this is a bullet item without one
first_text = item_texts[0] if item_texts else ""
is_bullet = len(item_line_indices) > 1 or _BULLET_RE.match(first_text)
if is_bullet and not _BULLET_RE.match(first_text) and row_idx > 0:
# Continuation item without bullet — add one
merged_text = "" + merged_text
cell = {
"cell_id": f"Z{zone_index}_R{row_idx}C0",
"row_index": row_idx,
"col_index": 0,
"col_type": "column_1",
"text": merged_text,
"word_boxes": item_words,
}
cells.append(cell)
# Detect header: first item if it has no continuation lines and is short
if len(items) >= 2:
first_item_texts = []
for li in items[0]:
if li < len(lines):
first_item_texts.append(" ".join(w.get("text", "") for w in lines[li]).strip())
first_text = " ".join(first_item_texts)
if (len(first_text) < 40
or first_text.isupper()
or first_text.rstrip().endswith(':')):
header_rows = [0]
return {
"columns": [column],
"rows": rows,
"cells": cells,
"header_rows": header_rows,
"box_layout_type": layout_type,
"box_grid_reviewed": False,
}
# Columnar: use standard grid builder with independent column detection
result = _build_zone_grid(
zone_words, box_x, box_y, box_w, box_h,
zone_index, img_w, img_h,
global_columns=None, # detect columns independently
)
# Colspan detection is now handled generically by _detect_colspan_cells
# in grid_editor_helpers.py (called inside _build_zone_grid).
result["box_layout_type"] = layout_type
result["box_grid_reviewed"] = False
return result