Docling/docling/utils/layout_postprocessor.py
Christoph Auer ec6cf6f7e8
feat: Introduce LayoutOptions to control layout postprocessing behaviour (#1870)
Signed-off-by: Christoph Auer <cau@zurich.ibm.com>
2025-07-04 15:36:13 +02:00

671 lines
24 KiB
Python

import bisect
import logging
import sys
from collections import defaultdict
from typing import Dict, List, Set, Tuple
from docling_core.types.doc import DocItemLabel, Size
from docling_core.types.doc.page import TextCell
from rtree import index
from docling.datamodel.base_models import BoundingBox, Cluster, Page
from docling.datamodel.pipeline_options import LayoutOptions
_log = logging.getLogger(__name__)
class UnionFind:
"""Efficient Union-Find data structure for grouping elements."""
def __init__(self, elements):
self.parent = {elem: elem for elem in elements}
self.rank = dict.fromkeys(elements, 0)
def find(self, x):
if self.parent[x] != x:
self.parent[x] = self.find(self.parent[x]) # Path compression
return self.parent[x]
def union(self, x, y):
root_x, root_y = self.find(x), self.find(y)
if root_x == root_y:
return
if self.rank[root_x] > self.rank[root_y]:
self.parent[root_y] = root_x
elif self.rank[root_x] < self.rank[root_y]:
self.parent[root_x] = root_y
else:
self.parent[root_y] = root_x
self.rank[root_x] += 1
def get_groups(self) -> Dict[int, List[int]]:
"""Returns groups as {root: [elements]}."""
groups = defaultdict(list)
for elem in self.parent:
groups[self.find(elem)].append(elem)
return groups
class SpatialClusterIndex:
"""Efficient spatial indexing for clusters using R-tree and interval trees."""
def __init__(self, clusters: List[Cluster]):
p = index.Property()
p.dimension = 2
self.spatial_index = index.Index(properties=p)
self.x_intervals = IntervalTree()
self.y_intervals = IntervalTree()
self.clusters_by_id: Dict[int, Cluster] = {}
for cluster in clusters:
self.add_cluster(cluster)
def add_cluster(self, cluster: Cluster):
bbox = cluster.bbox
self.spatial_index.insert(cluster.id, bbox.as_tuple())
self.x_intervals.insert(bbox.l, bbox.r, cluster.id)
self.y_intervals.insert(bbox.t, bbox.b, cluster.id)
self.clusters_by_id[cluster.id] = cluster
def remove_cluster(self, cluster: Cluster):
self.spatial_index.delete(cluster.id, cluster.bbox.as_tuple())
del self.clusters_by_id[cluster.id]
def find_candidates(self, bbox: BoundingBox) -> Set[int]:
"""Find potential overlapping cluster IDs using all indexes."""
spatial = set(self.spatial_index.intersection(bbox.as_tuple()))
x_candidates = self.x_intervals.find_containing(
bbox.l
) | self.x_intervals.find_containing(bbox.r)
y_candidates = self.y_intervals.find_containing(
bbox.t
) | self.y_intervals.find_containing(bbox.b)
return spatial.union(x_candidates).union(y_candidates)
def check_overlap(
self,
bbox1: BoundingBox,
bbox2: BoundingBox,
overlap_threshold: float,
containment_threshold: float,
) -> bool:
"""Check if two bboxes overlap sufficiently."""
if bbox1.area() <= 0 or bbox2.area() <= 0:
return False
iou = bbox1.intersection_over_union(bbox2)
containment1 = bbox1.intersection_over_self(bbox2)
containment2 = bbox2.intersection_over_self(bbox1)
return (
iou > overlap_threshold
or containment1 > containment_threshold
or containment2 > containment_threshold
)
class Interval:
"""Helper class for sortable intervals."""
def __init__(self, min_val: float, max_val: float, id: int):
self.min_val = min_val
self.max_val = max_val
self.id = id
def __lt__(self, other):
if isinstance(other, Interval):
return self.min_val < other.min_val
return self.min_val < other
class IntervalTree:
"""Memory-efficient interval tree for 1D overlap queries."""
def __init__(self):
self.intervals: List[Interval] = [] # Sorted by min_val
def insert(self, min_val: float, max_val: float, id: int):
interval = Interval(min_val, max_val, id)
bisect.insort(self.intervals, interval)
def find_containing(self, point: float) -> Set[int]:
"""Find all intervals containing the point."""
pos = bisect.bisect_left(self.intervals, point)
result = set()
# Check intervals starting before point
for interval in reversed(self.intervals[:pos]):
if interval.min_val <= point <= interval.max_val:
result.add(interval.id)
else:
break
# Check intervals starting at/after point
for interval in self.intervals[pos:]:
if point <= interval.max_val:
if interval.min_val <= point:
result.add(interval.id)
else:
break
return result
class LayoutPostprocessor:
"""Postprocesses layout predictions by cleaning up clusters and mapping cells."""
# Cluster type-specific parameters for overlap resolution
OVERLAP_PARAMS = {
"regular": {"area_threshold": 1.3, "conf_threshold": 0.05},
"picture": {"area_threshold": 2.0, "conf_threshold": 0.3},
"wrapper": {"area_threshold": 2.0, "conf_threshold": 0.2},
}
WRAPPER_TYPES = {
DocItemLabel.FORM,
DocItemLabel.KEY_VALUE_REGION,
DocItemLabel.TABLE,
DocItemLabel.DOCUMENT_INDEX,
}
SPECIAL_TYPES = WRAPPER_TYPES.union({DocItemLabel.PICTURE})
CONFIDENCE_THRESHOLDS = {
DocItemLabel.CAPTION: 0.5,
DocItemLabel.FOOTNOTE: 0.5,
DocItemLabel.FORMULA: 0.5,
DocItemLabel.LIST_ITEM: 0.5,
DocItemLabel.PAGE_FOOTER: 0.5,
DocItemLabel.PAGE_HEADER: 0.5,
DocItemLabel.PICTURE: 0.5,
DocItemLabel.SECTION_HEADER: 0.45,
DocItemLabel.TABLE: 0.5,
DocItemLabel.TEXT: 0.5, # 0.45,
DocItemLabel.TITLE: 0.45,
DocItemLabel.CODE: 0.45,
DocItemLabel.CHECKBOX_SELECTED: 0.45,
DocItemLabel.CHECKBOX_UNSELECTED: 0.45,
DocItemLabel.FORM: 0.45,
DocItemLabel.KEY_VALUE_REGION: 0.45,
DocItemLabel.DOCUMENT_INDEX: 0.45,
}
LABEL_REMAPPING = {
# DocItemLabel.DOCUMENT_INDEX: DocItemLabel.TABLE,
DocItemLabel.TITLE: DocItemLabel.SECTION_HEADER,
}
def __init__(
self, page: Page, clusters: List[Cluster], options: LayoutOptions
) -> None:
"""Initialize processor with page and clusters."""
self.cells = page.cells
self.page = page
self.page_size = page.size
self.all_clusters = clusters
self.options = options
self.regular_clusters = [
c for c in clusters if c.label not in self.SPECIAL_TYPES
]
self.special_clusters = [c for c in clusters if c.label in self.SPECIAL_TYPES]
# Build spatial indices once
self.regular_index = SpatialClusterIndex(self.regular_clusters)
self.picture_index = SpatialClusterIndex(
[c for c in self.special_clusters if c.label == DocItemLabel.PICTURE]
)
self.wrapper_index = SpatialClusterIndex(
[c for c in self.special_clusters if c.label in self.WRAPPER_TYPES]
)
def postprocess(self) -> Tuple[List[Cluster], List[TextCell]]:
"""Main processing pipeline."""
self.regular_clusters = self._process_regular_clusters()
self.special_clusters = self._process_special_clusters()
# Remove regular clusters that are included in wrappers
contained_ids = {
child.id
for wrapper in self.special_clusters
if wrapper.label in self.SPECIAL_TYPES
for child in wrapper.children
}
self.regular_clusters = [
c for c in self.regular_clusters if c.id not in contained_ids
]
# Combine and sort final clusters
final_clusters = self._sort_clusters(
self.regular_clusters + self.special_clusters, mode="id"
)
for cluster in final_clusters:
cluster.cells = self._sort_cells(cluster.cells)
# Also sort cells in children if any
for child in cluster.children:
child.cells = self._sort_cells(child.cells)
assert self.page.parsed_page is not None
self.page.parsed_page.textline_cells = self.cells
self.page.parsed_page.has_lines = len(self.cells) > 0
return final_clusters, self.cells
def _process_regular_clusters(self) -> List[Cluster]:
"""Process regular clusters with iterative refinement."""
clusters = [
c
for c in self.regular_clusters
if c.confidence >= self.CONFIDENCE_THRESHOLDS[c.label]
]
# Apply label remapping
for cluster in clusters:
if cluster.label in self.LABEL_REMAPPING:
cluster.label = self.LABEL_REMAPPING[cluster.label]
# Initial cell assignment
clusters = self._assign_cells_to_clusters(clusters)
# Remove clusters with no cells
clusters = [cluster for cluster in clusters if cluster.cells]
# Handle orphaned cells
unassigned = self._find_unassigned_cells(clusters)
if unassigned and self.options.create_orphan_clusters:
next_id = max((c.id for c in self.all_clusters), default=0) + 1
orphan_clusters = []
for i, cell in enumerate(unassigned):
conf = cell.confidence
orphan_clusters.append(
Cluster(
id=next_id + i,
label=DocItemLabel.TEXT,
bbox=cell.to_bounding_box(),
confidence=conf,
cells=[cell],
)
)
clusters.extend(orphan_clusters)
# Iterative refinement
prev_count = len(clusters) + 1
for _ in range(3): # Maximum 3 iterations
if prev_count == len(clusters):
break
prev_count = len(clusters)
clusters = self._adjust_cluster_bboxes(clusters)
clusters = self._remove_overlapping_clusters(clusters, "regular")
return clusters
def _process_special_clusters(self) -> List[Cluster]:
special_clusters = [
c
for c in self.special_clusters
if c.confidence >= self.CONFIDENCE_THRESHOLDS[c.label]
]
special_clusters = self._handle_cross_type_overlaps(special_clusters)
# Calculate page area from known page size
assert self.page_size is not None
page_area = self.page_size.width * self.page_size.height
if page_area > 0:
# Filter out full-page pictures
special_clusters = [
cluster
for cluster in special_clusters
if not (
cluster.label == DocItemLabel.PICTURE
and cluster.bbox.area() / page_area > 0.90
)
]
for special in special_clusters:
contained = []
for cluster in self.regular_clusters:
containment = cluster.bbox.intersection_over_self(special.bbox)
if containment > 0.8:
contained.append(cluster)
if contained:
# Sort contained clusters by minimum cell ID:
contained = self._sort_clusters(contained, mode="id")
special.children = contained
# Adjust bbox only for Form and Key-Value-Region, not Table or Picture
if special.label in [DocItemLabel.FORM, DocItemLabel.KEY_VALUE_REGION]:
special.bbox = BoundingBox(
l=min(c.bbox.l for c in contained),
t=min(c.bbox.t for c in contained),
r=max(c.bbox.r for c in contained),
b=max(c.bbox.b for c in contained),
)
# Collect all cells from children
all_cells = []
for child in contained:
all_cells.extend(child.cells)
special.cells = self._deduplicate_cells(all_cells)
special.cells = self._sort_cells(special.cells)
picture_clusters = [
c for c in special_clusters if c.label == DocItemLabel.PICTURE
]
picture_clusters = self._remove_overlapping_clusters(
picture_clusters, "picture"
)
wrapper_clusters = [
c for c in special_clusters if c.label in self.WRAPPER_TYPES
]
wrapper_clusters = self._remove_overlapping_clusters(
wrapper_clusters, "wrapper"
)
return picture_clusters + wrapper_clusters
def _handle_cross_type_overlaps(self, special_clusters) -> List[Cluster]:
"""Handle overlaps between regular and wrapper clusters before child assignment.
In particular, KEY_VALUE_REGION proposals that are almost identical to a TABLE
should be removed.
"""
wrappers_to_remove = set()
for wrapper in special_clusters:
if wrapper.label not in self.WRAPPER_TYPES:
continue # only treat KEY_VALUE_REGION for now.
for regular in self.regular_clusters:
if regular.label == DocItemLabel.TABLE:
# Calculate overlap
overlap_ratio = wrapper.bbox.intersection_over_self(regular.bbox)
conf_diff = wrapper.confidence - regular.confidence
# If wrapper is mostly overlapping with a TABLE, remove the wrapper
if (
overlap_ratio > 0.9 and conf_diff < 0.1
): # self.OVERLAP_PARAMS["wrapper"]["conf_threshold"]): # 80% overlap threshold
wrappers_to_remove.add(wrapper.id)
break
# Filter out the identified wrappers
special_clusters = [
cluster
for cluster in special_clusters
if cluster.id not in wrappers_to_remove
]
return special_clusters
def _should_prefer_cluster(
self, candidate: Cluster, other: Cluster, params: dict
) -> bool:
"""Determine if candidate cluster should be preferred over other cluster based on rules.
Returns True if candidate should be preferred, False if not."""
# Rule 1: LIST_ITEM vs TEXT
if (
candidate.label == DocItemLabel.LIST_ITEM
and other.label == DocItemLabel.TEXT
):
# Check if areas are similar (within 20% of each other)
area_ratio = candidate.bbox.area() / other.bbox.area()
area_similarity = abs(1 - area_ratio) < 0.2
if area_similarity:
return True
# Rule 2: CODE vs others
if candidate.label == DocItemLabel.CODE:
# Calculate how much of the other cluster is contained within the CODE cluster
containment = other.bbox.intersection_over_self(candidate.bbox)
if containment > 0.8: # other is 80% contained within CODE
return True
# If no label-based rules matched, fall back to area/confidence thresholds
area_ratio = candidate.bbox.area() / other.bbox.area()
conf_diff = other.confidence - candidate.confidence
if (
area_ratio <= params["area_threshold"]
and conf_diff > params["conf_threshold"]
):
return False
return True # Default to keeping candidate if no rules triggered rejection
def _select_best_cluster_from_group(
self,
group_clusters: List[Cluster],
params: dict,
) -> Cluster:
"""Select best cluster from a group of overlapping clusters based on all rules."""
current_best = None
for candidate in group_clusters:
should_select = True
for other in group_clusters:
if other == candidate:
continue
if not self._should_prefer_cluster(candidate, other, params):
should_select = False
break
if should_select:
if current_best is None:
current_best = candidate
else:
# If both clusters pass rules, prefer the larger one unless confidence differs significantly
if (
candidate.bbox.area() > current_best.bbox.area()
and current_best.confidence - candidate.confidence
<= params["conf_threshold"]
):
current_best = candidate
return current_best if current_best else group_clusters[0]
def _remove_overlapping_clusters(
self,
clusters: List[Cluster],
cluster_type: str,
overlap_threshold: float = 0.8,
containment_threshold: float = 0.8,
) -> List[Cluster]:
if not clusters:
return []
spatial_index = (
self.regular_index
if cluster_type == "regular"
else self.picture_index
if cluster_type == "picture"
else self.wrapper_index
)
# Map of currently valid clusters
valid_clusters = {c.id: c for c in clusters}
uf = UnionFind(valid_clusters.keys())
params = self.OVERLAP_PARAMS[cluster_type]
for cluster in clusters:
candidates = spatial_index.find_candidates(cluster.bbox)
candidates &= valid_clusters.keys() # Only keep existing candidates
candidates.discard(cluster.id)
for other_id in candidates:
if spatial_index.check_overlap(
cluster.bbox,
valid_clusters[other_id].bbox,
overlap_threshold,
containment_threshold,
):
uf.union(cluster.id, other_id)
result = []
for group in uf.get_groups().values():
if len(group) == 1:
result.append(valid_clusters[group[0]])
continue
group_clusters = [valid_clusters[cid] for cid in group]
best = self._select_best_cluster_from_group(group_clusters, params)
# Simple cell merging - no special cases
for cluster in group_clusters:
if cluster != best:
best.cells.extend(cluster.cells)
best.cells = self._deduplicate_cells(best.cells)
best.cells = self._sort_cells(best.cells)
result.append(best)
return result
def _select_best_cluster(
self,
clusters: List[Cluster],
area_threshold: float,
conf_threshold: float,
) -> Cluster:
"""Iteratively select best cluster based on area and confidence thresholds."""
current_best = None
for candidate in clusters:
should_select = True
for other in clusters:
if other == candidate:
continue
area_ratio = candidate.bbox.area() / other.bbox.area()
conf_diff = other.confidence - candidate.confidence
if area_ratio <= area_threshold and conf_diff > conf_threshold:
should_select = False
break
if should_select:
if current_best is None or (
candidate.bbox.area() > current_best.bbox.area()
and current_best.confidence - candidate.confidence <= conf_threshold
):
current_best = candidate
return current_best if current_best else clusters[0]
def _deduplicate_cells(self, cells: List[TextCell]) -> List[TextCell]:
"""Ensure each cell appears only once, maintaining order of first appearance."""
seen_ids = set()
unique_cells = []
for cell in cells:
if cell.index not in seen_ids:
seen_ids.add(cell.index)
unique_cells.append(cell)
return unique_cells
def _assign_cells_to_clusters(
self, clusters: List[Cluster], min_overlap: float = 0.2
) -> List[Cluster]:
"""Assign cells to best overlapping cluster."""
for cluster in clusters:
cluster.cells = []
for cell in self.cells:
if not cell.text.strip():
continue
best_overlap = min_overlap
best_cluster = None
for cluster in clusters:
if cell.rect.to_bounding_box().area() <= 0:
continue
overlap_ratio = cell.rect.to_bounding_box().intersection_over_self(
cluster.bbox
)
if overlap_ratio > best_overlap:
best_overlap = overlap_ratio
best_cluster = cluster
if best_cluster is not None:
best_cluster.cells.append(cell)
# Deduplicate cells in each cluster after assignment
for cluster in clusters:
cluster.cells = self._deduplicate_cells(cluster.cells)
return clusters
def _find_unassigned_cells(self, clusters: List[Cluster]) -> List[TextCell]:
"""Find cells not assigned to any cluster."""
assigned = {cell.index for cluster in clusters for cell in cluster.cells}
return [
cell
for cell in self.cells
if cell.index not in assigned and cell.text.strip()
]
def _adjust_cluster_bboxes(self, clusters: List[Cluster]) -> List[Cluster]:
"""Adjust cluster bounding boxes to contain their cells."""
for cluster in clusters:
if not cluster.cells:
continue
cells_bbox = BoundingBox(
l=min(cell.rect.to_bounding_box().l for cell in cluster.cells),
t=min(cell.rect.to_bounding_box().t for cell in cluster.cells),
r=max(cell.rect.to_bounding_box().r for cell in cluster.cells),
b=max(cell.rect.to_bounding_box().b for cell in cluster.cells),
)
if cluster.label == DocItemLabel.TABLE:
# For tables, take union of current bbox and cells bbox
cluster.bbox = BoundingBox(
l=min(cluster.bbox.l, cells_bbox.l),
t=min(cluster.bbox.t, cells_bbox.t),
r=max(cluster.bbox.r, cells_bbox.r),
b=max(cluster.bbox.b, cells_bbox.b),
)
else:
cluster.bbox = cells_bbox
return clusters
def _sort_cells(self, cells: List[TextCell]) -> List[TextCell]:
"""Sort cells in native reading order."""
return sorted(cells, key=lambda c: (c.index))
def _sort_clusters(
self, clusters: List[Cluster], mode: str = "id"
) -> List[Cluster]:
"""Sort clusters in reading order (top-to-bottom, left-to-right)."""
if mode == "id": # sort in the order the cells are printed in the PDF.
return sorted(
clusters,
key=lambda cluster: (
(
min(cell.index for cell in cluster.cells)
if cluster.cells
else sys.maxsize
),
cluster.bbox.t,
cluster.bbox.l,
),
)
elif mode == "tblr": # Sort top-to-bottom, then left-to-right ("row first")
return sorted(
clusters, key=lambda cluster: (cluster.bbox.t, cluster.bbox.l)
)
elif mode == "lrtb": # Sort left-to-right, then top-to-bottom ("column first")
return sorted(
clusters, key=lambda cluster: (cluster.bbox.l, cluster.bbox.t)
)
else:
return clusters