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import logging
import random
from io import BytesIO
from pathlib import Path
from typing import TYPE_CHECKING, Iterable, List, Optional, Union
import pypdfium2 as pdfium
import pypdfium2.raw as pdfium_c
from docling_core.types.doc import BoundingBox, CoordOrigin, Size
from PIL import Image, ImageDraw
from pypdfium2 import PdfTextPage
from pypdfium2._helpers.misc import PdfiumError
from docling.backend.pdf_backend import PdfDocumentBackend, PdfPageBackend
from docling.datamodel.base_models import Cell
if TYPE_CHECKING:
from docling.datamodel.document import InputDocument
_log = logging.getLogger(__name__)
class PyPdfiumPageBackend(PdfPageBackend):
def __init__(
self, pdfium_doc: pdfium.PdfDocument, document_hash: str, page_no: int
):
self.valid = True # No better way to tell from pypdfium.
try:
self._ppage: pdfium.PdfPage = pdfium_doc[page_no]
except PdfiumError as e:
_log.info(
f"An exception occurred when loading page {page_no} of document {document_hash}.",
exc_info=True,
)
self.valid = False
self.text_page: Optional[PdfTextPage] = None
def is_valid(self) -> bool:
return self.valid
def get_bitmap_rects(self, scale: float = 1) -> Iterable[BoundingBox]:
AREA_THRESHOLD = 0 # 32 * 32
for obj in self._ppage.get_objects(filter=[pdfium_c.FPDF_PAGEOBJ_IMAGE]):
pos = obj.get_pos()
cropbox = BoundingBox.from_tuple(
pos, origin=CoordOrigin.BOTTOMLEFT
).to_top_left_origin(page_height=self.get_size().height)
if cropbox.area() > AREA_THRESHOLD:
cropbox = cropbox.scaled(scale=scale)
yield cropbox
def get_text_in_rect(self, bbox: BoundingBox) -> str:
if not self.text_page:
self.text_page = self._ppage.get_textpage()
if bbox.coord_origin != CoordOrigin.BOTTOMLEFT:
bbox = bbox.to_bottom_left_origin(self.get_size().height)
text_piece = self.text_page.get_text_bounded(*bbox.as_tuple())
return text_piece
def get_text_cells(self) -> Iterable[Cell]:
if not self.text_page:
self.text_page = self._ppage.get_textpage()
cells = []
cell_counter = 0
page_size = self.get_size()
for i in range(self.text_page.count_rects()):
rect = self.text_page.get_rect(i)
text_piece = self.text_page.get_text_bounded(*rect)
x0, y0, x1, y1 = rect
cells.append(
Cell(
id=cell_counter,
text=text_piece,
bbox=BoundingBox(
l=x0, b=y0, r=x1, t=y1, coord_origin=CoordOrigin.BOTTOMLEFT
).to_top_left_origin(page_size.height),
)
)
cell_counter += 1
# PyPdfium2 produces very fragmented cells, with sub-word level boundaries, in many PDFs.
# The cell merging code below is to clean this up.
def merge_horizontal_cells(
cells: List[Cell],
horizontal_threshold_factor: float = 1.0,
vertical_threshold_factor: float = 0.5,
) -> List[Cell]:
if not cells:
return []
def group_rows(cells: List[Cell]) -> List[List[Cell]]:
rows = []
current_row = [cells[0]]
row_top = cells[0].bbox.t
row_bottom = cells[0].bbox.b
row_height = cells[0].bbox.height
for cell in cells[1:]:
vertical_threshold = row_height * vertical_threshold_factor
if (
abs(cell.bbox.t - row_top) <= vertical_threshold
and abs(cell.bbox.b - row_bottom) <= vertical_threshold
):
current_row.append(cell)
row_top = min(row_top, cell.bbox.t)
row_bottom = max(row_bottom, cell.bbox.b)
row_height = row_bottom - row_top
else:
rows.append(current_row)
current_row = [cell]
row_top = cell.bbox.t
row_bottom = cell.bbox.b
row_height = cell.bbox.height
if current_row:
rows.append(current_row)
return rows
def merge_row(row: List[Cell]) -> List[Cell]:
merged = []
current_group = [row[0]]
for cell in row[1:]:
prev_cell = current_group[-1]
avg_height = (prev_cell.bbox.height + cell.bbox.height) / 2
if (
cell.bbox.l - prev_cell.bbox.r
<= avg_height * horizontal_threshold_factor
):
current_group.append(cell)
else:
merged.append(merge_group(current_group))
current_group = [cell]
if current_group:
merged.append(merge_group(current_group))
return merged
def merge_group(group: List[Cell]) -> Cell:
if len(group) == 1:
return group[0]
merged_text = "".join(cell.text for cell in group)
merged_bbox = BoundingBox(
l=min(cell.bbox.l for cell in group),
t=min(cell.bbox.t for cell in group),
r=max(cell.bbox.r for cell in group),
b=max(cell.bbox.b for cell in group),
)
return Cell(id=group[0].id, text=merged_text, bbox=merged_bbox)
rows = group_rows(cells)
merged_cells = [cell for row in rows for cell in merge_row(row)]
for i, cell in enumerate(merged_cells, 1):
cell.id = i
return merged_cells
def draw_clusters_and_cells():
image = (
self.get_page_image()
) # make new image to avoid drawing on the saved ones
draw = ImageDraw.Draw(image)
for c in cells:
x0, y0, x1, y1 = c.bbox.as_tuple()
cell_color = (
random.randint(30, 140),
random.randint(30, 140),
random.randint(30, 140),
)
draw.rectangle([(x0, y0), (x1, y1)], outline=cell_color)
image.show()
# before merge:
# draw_clusters_and_cells()
cells = merge_horizontal_cells(cells)
# after merge:
# draw_clusters_and_cells()
return cells
def get_page_image(
self, scale: float = 1, cropbox: Optional[BoundingBox] = None
) -> Image.Image:
page_size = self.get_size()
if not cropbox:
cropbox = BoundingBox(
l=0,
r=page_size.width,
t=0,
b=page_size.height,
coord_origin=CoordOrigin.TOPLEFT,
)
padbox = BoundingBox(
l=0, r=0, t=0, b=0, coord_origin=CoordOrigin.BOTTOMLEFT
)
else:
padbox = cropbox.to_bottom_left_origin(page_size.height).model_copy()
padbox.r = page_size.width - padbox.r
padbox.t = page_size.height - padbox.t
image = (
self._ppage.render(
scale=scale * 1.5,
rotation=0, # no additional rotation
crop=padbox.as_tuple(),
)
.to_pil()
.resize(size=(round(cropbox.width * scale), round(cropbox.height * scale)))
) # We resize the image from 1.5x the given scale to make it sharper.
return image
def get_size(self) -> Size:
return Size(width=self._ppage.get_width(), height=self._ppage.get_height())
def unload(self):
self._ppage = None
self.text_page = None
class PyPdfiumDocumentBackend(PdfDocumentBackend):
def __init__(self, in_doc: "InputDocument", path_or_stream: Union[BytesIO, Path]):
super().__init__(in_doc, path_or_stream)
try:
self._pdoc = pdfium.PdfDocument(self.path_or_stream)
except PdfiumError as e:
raise RuntimeError(
f"pypdfium could not load document with hash {self.document_hash}"
) from e
def page_count(self) -> int:
return len(self._pdoc)
def load_page(self, page_no: int) -> PyPdfiumPageBackend:
return PyPdfiumPageBackend(self._pdoc, self.document_hash, page_no)
def is_valid(self) -> bool:
return self.page_count() > 0
def unload(self):
super().unload()
self._pdoc.close()
self._pdoc = None
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