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fix: Improve OCR results, stricten criteria before dropping bitmap areas (#719)

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fix: Properly care for all bitmap elements in OCR

Signed-off-by: Christoph Auer <cau@zurich.ibm.com>
This commit is contained in:
Christoph Auer
2025-01-10 10:38:49 +01:00
committed by GitHub
parent 9a6b5c8c8d
commit 5a060f237d
5 changed files with 19 additions and 16 deletions
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27
docling/models/base_ocr_model.py
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@@ -8,7 +8,7 @@ import numpy as np
from docling_core.types.doc import BoundingBox, CoordOrigin
from PIL import Image, ImageDraw
from rtree import index
from scipy.ndimage import find_objects, label
from scipy.ndimage import binary_dilation, find_objects, label
from docling.datamodel.base_models import Cell, OcrCell, Page
from docling.datamodel.document import ConversionResult
@@ -43,6 +43,12 @@ class BaseOcrModel(BasePageModel):
np_image = np.array(image)
# Dilate the image by 10 pixels to merge nearby bitmap rectangles
structure = np.ones(
(20, 20)
) # Create a 20x20 structure element (10 pixels in all directions)
np_image = binary_dilation(np_image > 0, structure=structure)
# Find the connected components
labeled_image, num_features = label(
np_image > 0
@@ -72,7 +78,7 @@ class BaseOcrModel(BasePageModel):
bitmap_rects = []
coverage, ocr_rects = find_ocr_rects(page.size, bitmap_rects)
# return full-page rectangle if sufficiently covered with bitmaps
# return full-page rectangle if page is dominantly covered with bitmaps
if self.options.force_full_page_ocr or coverage > max(
BITMAP_COVERAGE_TRESHOLD, self.options.bitmap_area_threshold
):
@@ -85,17 +91,11 @@ class BaseOcrModel(BasePageModel):
coord_origin=CoordOrigin.TOPLEFT,
)
]
# return individual rectangles if the bitmap coverage is smaller
else: # coverage <= BITMAP_COVERAGE_TRESHOLD:
# skip OCR if the bitmap area on the page is smaller than the options threshold
ocr_rects = [
rect
for rect in ocr_rects
if rect.area() / (page.size.width * page.size.height)
> self.options.bitmap_area_threshold
]
# return individual rectangles if the bitmap coverage is above the threshold
elif coverage > self.options.bitmap_area_threshold:
return ocr_rects
else: # overall coverage of bitmaps is too low, drop all bitmap rectangles.
return []
# Filters OCR cells by dropping any OCR cell that intersects with an existing programmatic cell.
def _filter_ocr_cells(self, ocr_cells, programmatic_cells):
@@ -162,6 +162,9 @@ class BaseOcrModel(BasePageModel):
x0 *= scale_x
x1 *= scale_x
if y1 <= y0:
y1, y0 = y0, y1
color = "gray"
if isinstance(tc, OcrCell):
color = "magenta"