Further exploratory improvements
This commit is contained in:
James R. Barlow
@@ -16,6 +16,8 @@ from pathlib import Path
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from typing import Any, NamedTuple
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from xml.etree import ElementTree
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from pikepdf import PdfMatrix
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from ocrmypdf.hocrtransform.backends import (
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Canvas,
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)
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@@ -97,6 +99,19 @@ class Rect(NamedTuple):
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x2: Any
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y2: Any
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def transform(self, matrix, inverse=True):
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"""Transform the rectangle by the given matrix."""
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if inverse:
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matrix = matrix.inverse()
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return Rect._make(
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[
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matrix.a * self.x1 + matrix.c * self.y1 + matrix.e,
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matrix.b * self.x1 + matrix.d * self.y1 + matrix.f,
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matrix.a * self.x2 + matrix.c * self.y2 + matrix.e,
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matrix.b * self.x2 + matrix.d * self.y2 + matrix.f,
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]
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)
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class HocrTransformError(Exception):
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"""Error while applying hOCR transform."""
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@@ -332,12 +347,15 @@ class HocrTransform:
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cos_a, sin_a = cos(angle), sin(angle)
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intercept = pxl_intercept / self.dpi * inch
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# Matrix it!
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# pdf._cs.push()
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# pdf._cs.cm(cos_a, -sin_a, sin_a, cos_a, 0, 0)
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# cos_a, sin_a = 1, 0
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# slope = 0
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# intercept = 0
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# Enter a new coordinate system with the linebox at the origin
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pdf._cs.push()
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line_matrix = PdfMatrix().translated(line_box.x1, line_box.y1).rotated(-angle)
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pdf._cs.cm(*line_matrix.shorthand)
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cos_a, sin_a = 1, 0
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slope = 0
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intercept = 0
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cm_line_box = line_box.transform(line_matrix, inverse=True)
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text = pdf.begin_text()
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@@ -352,7 +370,7 @@ class HocrTransform:
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# Intercept is normally negative. Subtracting it will raise the baseline
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# above the bottom of the bounding box (y1). We're in page coordinates,
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# origin bottom left, y2 > y1.
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baseline_y1 = line_box.y1 - intercept
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baseline_y1 = -intercept
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if show_bounding_boxes and True: # pragma: no cover
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# draw the baseline in magenta, dashed
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@@ -362,12 +380,12 @@ class HocrTransform:
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# negate slope because it is defined as a rise/run in pixel
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# coordinates and page coordinates have the y axis flipped
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pdf.line(
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line_box.x1,
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cm_line_box.x1,
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baseline_y1,
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line_box.x2,
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self.polyval((-slope, baseline_y1), line_box.x2 - line_box.x1),
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cm_line_box.x2,
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self.polyval((-slope, baseline_y1), cm_line_box.x2 - cm_line_box.x1),
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)
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text.set_text_transform(cos_a, -sin_a, sin_a, cos_a, line_box.x1, baseline_y1)
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text.set_text_transform(1, 0, 0, 1, line_box.x1, baseline_y1)
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pdf.set_fill_color(black) # text in black
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elements = line.findall(self._child_xpath('span', elemclass))
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@@ -379,6 +397,7 @@ class HocrTransform:
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pxl_coords = self.element_coordinates(elem)
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box = self.pt_from_pixel(pxl_coords, bottomup=True)
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cm_box = box.transform(line_matrix, inverse=True)
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if interword_spaces:
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# if `--interword-spaces` is true, append a space
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# to the end of each text element to allow simpler PDF viewers
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@@ -387,15 +406,15 @@ class HocrTransform:
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# though it would look better, because it will interfere with
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# naive text extraction. \n does not work either.
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elemtxt += ' '
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box = Rect._make(
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cm_box = Rect._make(
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(
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box.x1,
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line_box.y1,
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box.x2 + pdf.string_width(' ', fontname, line_height),
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line_box.y2,
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cm_box.x1,
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cm_line_box.y1,
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cm_box.x2, # + pdf.string_width(' ', fontname, line_height),
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cm_line_box.y2,
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)
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)
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box_width = box.x2 - box.x1
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box_width = cm_box.x2 - cm_box.x1
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font_width = pdf.string_width(elemtxt, fontname, fontsize)
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# draw the bbox border
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@@ -405,14 +424,16 @@ class HocrTransform:
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pdf.set_line_width(0.1)
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# Draw a triangle that conveys word height and drawing direction
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if True:
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pdf.line(box.x1, box.y1, box.x2, box.y1) # across bottom
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pdf.line(box.x2, box.y1, box.x1, box.y2) # diagonal
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pdf.line(box.x1, box.y1, box.x1, box.y2) # rise
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pdf.line(
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cm_box.x1, cm_box.y1, cm_box.x2, cm_box.y1
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) # across bottom
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pdf.line(cm_box.x2, cm_box.y1, cm_box.x1, cm_box.y2) # diagonal
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pdf.line(cm_box.x1, cm_box.y1, cm_box.x1, cm_box.y2) # rise
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pdf.set_dashes()
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pdf.set_stroke_color(green)
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pdf.set_line_width(0.1)
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pdf.rect(box.x1, line_box.y1, box_width, line_height, fill=0)
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pdf.rect(cm_box.x1, cm_line_box.y1, box_width, line_height, fill=0)
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# Adjust relative position of cursor
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# This is equivalent to:
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@@ -432,12 +453,12 @@ class HocrTransform:
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dy = baseline_y1 - cursor[1]
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text.move_cursor(dx, dy)
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text.set_text_transform(
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cos_a,
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-sin_a,
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sin_a,
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cos_a,
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box.x1,
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line_box.y1,
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1,
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0,
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0,
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1,
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cm_box.x1,
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cm_line_box.y1,
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)
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# If reportlab tells us this word is 0 units wide, our best seems
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@@ -446,7 +467,7 @@ class HocrTransform:
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text.set_horiz_scale(100 * box_width / font_width)
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text.show(elemtxt)
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pdf.draw_text(text)
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# pdf._cs.pop()
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pdf._cs.pop()
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if __name__ == "__main__":
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