menekis/OCRmyPDF
Public Access
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Tidying new hOCR renderer

Browse Source
This commit is contained in:
James R. Barlow
2023-11-19 23:51:27 -08:00
parent 415de77457
commit b14f6f778a
1 changed files with 49 additions and 75 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/ocrmypdf/hocrtransform/__init__.py
+49 -75
View File
@@ -9,6 +9,7 @@
from __future__ import annotations
import argparse
import logging
import os
import re
import unicodedata
@@ -21,7 +22,8 @@ from xml.etree import ElementTree
from pikepdf import Matrix, Rectangle
from ocrmypdf.hocrtransform._canvas import PikepdfCanvas, PikepdfText
from ocrmypdf.hocrtransform._canvas import PikepdfCanvas as Canvas
from ocrmypdf.hocrtransform._canvas import PikepdfText
from ocrmypdf.hocrtransform.color import (
BLACK,
BLUE,
@@ -31,6 +33,8 @@ from ocrmypdf.hocrtransform.color import (
RED,
)
log = logging.getLogger(__name__)
INCH = 72.0
Element = ElementTree.Element
@@ -67,9 +71,6 @@ class HocrTransform:
([\-\+]?\d+) # +/- int''',
re.VERBOSE,
)
ligatures = str.maketrans(
{'ff': 'ff', 'ffi': 'f‌f‌i', 'ffl': 'f‌f‌l', 'fi': 'fi', 'fl': 'fl'}
)
def __init__(self, *, hocr_filename: str | Path, dpi: float):
"""Initialize the HocrTransform object."""
@@ -95,23 +96,13 @@ class HocrTransform:
raise HocrTransformError("hocr file is missing page dimensions")
self.render_options = DebugRenderOptions(
render_baseline=True,
render_triangle=False,
render_line_bbox=False,
render_triangle=True,
render_line_bbox=True,
render_word_bbox=True,
render_paragraph_bbox=False,
render_paragraph_bbox=True,
render_space_bbox=False,
)
def __str__(self): # pragma: no cover
"""Return the textual content of the HTML body."""
if self.hocr is None:
return ''
body = self.hocr.find(self._child_xpath('body'))
if body:
return self._get_element_text(body)
else:
return ''
def _get_element_text(self, element: Element):
"""Return the textual content of the element and its children."""
text = ''
@@ -152,11 +143,6 @@ class HocrTransform:
xpath += f"[@class='{html_class}']"
return xpath
@classmethod
def replace_unsupported_chars(cls, s: str) -> str:
"""Replaces characters with those available in the Helvetica typeface."""
return s.translate(cls.ligatures)
@classmethod
def normalize_text(cls, s: str) -> str:
"""Normalize the given text using the NFKC normalization form."""
@@ -184,19 +170,14 @@ class HocrTransform:
out_filename: Path of PDF to write.
image_filename: Image to use for this file. If omitted, the OCR text
is shown.
show_bounding_boxes: Show bounding boxes around various text regions,
for debugging.
fontname: Name of font to use.
invisible_text: If True, text is rendered invisible so that is
selectable but never drawn. If False, text is visible and may
be seen if the image is skipped or deleted in Acrobat.
interword_spaces: If True, insert spaces between words rather than
drawing each word without spaces. Generally this improves text
extraction.
"""
# create the PDF file
# page size in points (1/72 in.)
canvas = PikepdfCanvas(
canvas = Canvas(
out_filename,
page_size=(self.width, self.height),
)
@@ -208,22 +189,9 @@ class HocrTransform:
.scaled(INCH / self.dpi, INCH / self.dpi)
)
canvas.cm(page_matrix)
print(page_matrix)
log.debug(page_matrix)
for elem in self.hocr.iterfind(self._child_xpath('p', 'ocr_par')):
elemtxt = self._get_element_text(elem).rstrip()
if len(elemtxt) == 0:
continue
ocr_par = self.element_coordinates(elem)
# draw cyan box around paragraph
if self.render_options.render_paragraph_bbox:
# pragma: no cover
canvas.set_stroke_color(CYAN)
canvas.set_line_width(0.1) # no line for bounding box
canvas.rect(
ocr_par.llx, ocr_par.lly, ocr_par.width, ocr_par.height, fill=0
)
self._debug_draw_paragraph_boxes(canvas)
found_lines = False
for line in (
@@ -239,7 +207,6 @@ class HocrTransform:
"ocrx_word",
fontname,
invisible_text,
interword_spaces,
)
if not found_lines:
@@ -251,7 +218,6 @@ class HocrTransform:
"ocrx_word",
fontname,
invisible_text,
interword_spaces,
)
canvas.pop()
# put the image on the page, scaled to fill the page
@@ -270,19 +236,18 @@ class HocrTransform:
def _do_line(
self,
canvas: PikepdfCanvas,
canvas: Canvas,
line: Element | None,
elemclass: str,
fontname: str,
invisible_text: bool,
interword_spaces: bool,
):
if line is None:
return
line_box = self.element_coordinates(line)
assert line_box.ury > line_box.lly # lly is top, ury is bottom
self._do_debug_line_bbox(canvas, line_box)
self._debug_draw_line_bbox(canvas, line_box)
# Baseline is a polynomial (usually straight line) in the coordinate system
# of the line
@@ -301,7 +266,7 @@ class HocrTransform:
.rotated(angle / pi * 180)
)
canvas.cm(line_matrix)
print(line_matrix)
log.debug(line_matrix)
text = canvas.begin_text()
# Don't allow the font to break out of the bounding box. Division by
@@ -313,7 +278,7 @@ class HocrTransform:
if invisible_text or True:
text.set_render_mode(3) # Invisible (indicates OCR text)
self._do_debug_baseline(canvas, line_matrix.inverse().transform(line_box), 0)
self._debug_draw_baseline(canvas, line_matrix.inverse().transform(line_box), 0)
canvas.set_fill_color(BLACK) # text in black
elements = line.findall(self._child_xpath('span', elemclass))
@@ -334,7 +299,7 @@ class HocrTransform:
def _do_line_word(
self,
canvas: PikepdfCanvas,
canvas: Canvas,
fontname,
line_matrix: Matrix,
line_height: float,
@@ -356,11 +321,10 @@ class HocrTransform:
font_width = canvas.string_width(elemtxt, fontname, fontsize)
# Debug sketches
self._do_debug_word_triangle(canvas, box)
self._do_debug_word_bbox(
self._debug_draw_word_triangle(canvas, box)
self._debug_draw_word_bbox(
canvas,
box.height,
line_matrix.inverse().transform(line_box),
box,
box.width,
)
@@ -374,19 +338,33 @@ class HocrTransform:
if next_elem is not None:
next_box = self.element_coordinates(next_elem)
space_box = Rectangle(box.urx, line_box.lly, next_box.llx, line_box.ury)
self._do_debug_space_bbox(canvas, space_box)
self._debug_draw_space_bbox(canvas, space_box)
text.set_text_transform(Matrix(1, 0, 0, 1, space_box.llx, 0))
space_width = canvas.string_width(' ', fontname, fontsize)
space_box_width = space_box.urx - space_box.llx
text.set_horiz_scale(100 * space_box_width / space_width)
text.show(' ')
def _do_debug_line_bbox(self, canvas, line_box):
def _debug_draw_paragraph_boxes(self, canvas: Canvas, color=CYAN):
"""Draw boxes around paragraphs in the document."""
if not self.render_options.render_paragraph_bbox: # pragma: no cover
return
for elem in self.hocr.iterfind(self._child_xpath('p', 'ocr_par')):
elemtxt = self._get_element_text(elem).rstrip()
if len(elemtxt) == 0:
continue
ocr_par = self.element_coordinates(elem)
# draw box around paragraph
canvas.set_stroke_color(color)
canvas.set_line_width(0.1) # no line for bounding box
canvas.rect(ocr_par.llx, ocr_par.lly, ocr_par.width, ocr_par.height, fill=0)
def _debug_draw_line_bbox(self, canvas, line_box, color=BLUE):
"""Render the bounding box of a text line."""
if not self.render_options.render_line_bbox: # pragma: no cover
return
canvas.push()
canvas.set_dashes()
canvas.set_stroke_color(BLUE)
canvas.set_stroke_color(color)
canvas.set_line_width(0.15)
canvas.rect(
line_box.llx,
@@ -397,16 +375,12 @@ class HocrTransform:
)
canvas.pop()
def _do_debug_word_triangle(
self,
canvas: PikepdfCanvas,
box,
):
def _debug_draw_word_triangle(self, canvas: Canvas, box, color=RED):
"""Render a triangle that conveys word height and drawing direction."""
if not self.render_options.render_triangle: # pragma: no cover
return
canvas.push()
canvas.set_dashes()
canvas.set_stroke_color(RED)
canvas.set_stroke_color(color)
canvas.set_line_width(0.1)
# Draw a triangle that conveys word height and drawing direction
canvas.line(box.llx, box.lly, box.urx, box.lly) # across bottom
@@ -414,37 +388,37 @@ class HocrTransform:
canvas.line(box.llx, box.lly, box.llx, box.ury) # rise
canvas.pop()
def _do_debug_word_bbox(
self, canvas: PikepdfCanvas, line_height, line_box, box, box_width
def _debug_draw_word_bbox(
self, canvas: Canvas, line_height, box, box_width, color=GREEN
):
"""Render a box depicting the word."""
if not self.render_options.render_word_bbox: # pragma: no cover
return
canvas.push()
canvas.set_dashes()
canvas.set_stroke_color(GREEN)
canvas.set_stroke_color(color)
canvas.set_line_width(0.1)
canvas.rect(box.llx, box.lly, box_width, line_height, fill=0)
canvas.pop()
def _do_debug_space_bbox(self, canvas: PikepdfCanvas, box):
def _debug_draw_space_bbox(self, canvas: Canvas, box, color=GREEN):
"""Render a box depicting the space between two words."""
if not self.render_options.render_space_bbox: # pragma: no cover
return
canvas.push()
canvas.set_dashes()
canvas.set_fill_color(GREEN)
canvas.set_fill_color(color)
canvas.set_line_width(0.1)
canvas.rect(box.llx, box.lly, box.width, box.height, fill=1)
canvas.pop()
def _do_debug_baseline(self, canvas, line_box, baseline_lly):
def _debug_draw_baseline(self, canvas, line_box, baseline_lly, color=MAGENTA):
"""Render the text baseline."""
if not self.render_options.render_baseline:
return
# draw the baseline in magenta, dashed
canvas.set_dashes()
canvas.set_stroke_color(MAGENTA)
canvas.set_stroke_color(color)
canvas.set_line_width(0.25)
# negate slope because it is defined as a rise/run in pixel
# coordinates and page coordinates have the y axis flipped
canvas.line(
line_box.llx,
baseline_lly,