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Refactor; accumulate content stream as bytes rather than discrete pikepdf objects

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This commit is contained in:
James R. Barlow
2023-11-20 22:11:59 -08:00
parent 73f8f6aac8
commit c69823f496
2 changed files with 81 additions and 51 deletions
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src/ocrmypdf/hocrtransform/_canvas.py
+73 -43
View File
@@ -22,6 +22,8 @@ from pikepdf import (
)
from PIL import Image
from .color import Color
log = logging.getLogger(__name__)
GLYPHLESS_FONT_NAME = 'pdf.ttf'
@@ -114,37 +116,43 @@ def register_glyphlessfont(pdf: Pdf):
class ContentStreamBuilder:
def __init__(self, instructions=None):
self._instructions: list[ContentStreamInstruction] = instructions or []
def __init__(self):
self._stream = b""
def _append(self, inst: ContentStreamInstruction):
self._stream += unparse_content_stream([inst]) + b"\n"
def extend(self, other: ContentStreamBuilder):
self._stream += other._stream
def push(self):
"""Save the graphics state."""
inst = ContentStreamInstruction([], Operator("q"))
self._instructions.append(inst)
self._append(inst)
return self
def pop(self):
"""Restore the graphics state."""
inst = ContentStreamInstruction([], Operator("Q"))
self._instructions.append(inst)
self._append(inst)
return self
def cm(self, matrix: Matrix):
"""Concatenate matrix."""
inst = ContentStreamInstruction(matrix.shorthand, Operator("cm"))
self._instructions.append(inst)
self._append(inst)
return self
def begin_text(self):
"""Begin text object."""
inst = ContentStreamInstruction([], Operator("BT"))
self._instructions.append(inst)
self._append(inst)
return self
def end_text(self):
"""End text object."""
inst = ContentStreamInstruction([], Operator("ET"))
self._instructions.append(inst)
self._append(inst)
return self
def begin_marked_content_proplist(self, mctype: Name, mcid: int):
@@ -152,92 +160,92 @@ class ContentStreamBuilder:
inst = ContentStreamInstruction(
[mctype, Dictionary(MCID=mcid)], Operator("BDC")
)
self._instructions.append(inst)
self._append(inst)
return self
def begin_marked_content(self, mctype: Name):
"""Begin marked content sequence."""
inst = ContentStreamInstruction([mctype], Operator("BMC"))
self._instructions.append(inst)
self._append(inst)
return self
def end_marked_content(self):
"""End marked content sequence."""
inst = ContentStreamInstruction([], Operator("EMC"))
self._instructions.append(inst)
self._append(inst)
return self
def set_text_font(self, font: Name, size: int):
"""Set text font and size."""
inst = ContentStreamInstruction([font, size], Operator("Tf"))
self._instructions.append(inst)
self._append(inst)
return self
def set_text_matrix(self, matrix: Matrix):
"""Set text matrix."""
inst = ContentStreamInstruction(matrix.shorthand, Operator("Tm"))
self._instructions.append(inst)
self._append(inst)
return self
def set_text_rendering(self, mode: int):
"""Set text rendering mode."""
inst = ContentStreamInstruction([mode], Operator("Tr"))
self._instructions.append(inst)
self._append(inst)
return self
def set_text_horizontal_scaling(self, scale: float):
"""Set text horizontal scaling."""
inst = ContentStreamInstruction([scale], Operator("Tz"))
self._instructions.append(inst)
self._append(inst)
return self
def show_text(self, text: str):
"""Show text."""
encoded = text.encode("utf-16be")
inst = ContentStreamInstruction([[encoded]], Operator("TJ"))
self._instructions.append(inst)
self._append(inst)
return self
def move_cursor(self, dx, dy):
"""Move cursor."""
inst = ContentStreamInstruction([dx, dy], Operator("Td"))
self._instructions.append(inst)
self._append(inst)
return self
def stroke_and_close(self):
"""Stroke and close path."""
inst = ContentStreamInstruction([], Operator("s"))
self._instructions.append(inst)
self._append(inst)
return self
def fill(self):
"""Stroke and close path."""
inst = ContentStreamInstruction([], Operator("f"))
self._instructions.append(inst)
self._append(inst)
return self
def append_rectangle(self, x: float, y: float, w: float, h: float):
"""Append rectangle to path."""
inst = ContentStreamInstruction([x, y, w, h], Operator("re"))
self._instructions.append(inst)
self._append(inst)
return self
def set_stroke_color(self, r: float, g: float, b: float):
"""Set RGB stroke color."""
inst = ContentStreamInstruction([r, g, b], Operator("RG"))
self._instructions.append(inst)
self._append(inst)
return self
def set_fill_color(self, r: float, g: float, b: float):
"""Set RGB fill color."""
inst = ContentStreamInstruction([r, g, b], Operator("rg"))
self._instructions.append(inst)
self._append(inst)
return self
def set_line_width(self, width):
"""Set line width."""
inst = ContentStreamInstruction([width], Operator("w"))
self._instructions.append(inst)
self._append(inst)
return self
def line(self, x1: float, y1: float, x2: float, y2: float):
@@ -246,7 +254,8 @@ class ContentStreamBuilder:
ContentStreamInstruction([x1, y1], Operator("m")),
ContentStreamInstruction([x2, y2], Operator("l")),
]
self._instructions.extend(insts)
self._append(insts[0])
self._append(insts[1])
return self
def set_dashes(self, array=None, phase=0):
@@ -257,16 +266,16 @@ class ContentStreamBuilder:
array = (array, phase)
phase = 0
inst = ContentStreamInstruction([array, phase], Operator("d"))
self._instructions.append(inst)
self._append(inst)
return self
def draw_form_xobject(self, name: Name):
inst = ContentStreamInstruction([name], Operator("Do"))
self._instructions.append(inst)
self._append(inst)
return self
def build(self):
return self._instructions
return self._stream
@dataclass
@@ -275,32 +284,39 @@ class LoadedImage:
image: Image.Image
class PikepdfCanvasAccessor:
class _PikepdfCanvasAccessor:
"""Support class for drawing on a pikepdf canvas."""
def __init__(self, cs: ContentStreamBuilder, images=None):
self._cs = cs
self._images = images if images is not None else []
self._stack_depth = 0
def stroke_color(self, color):
def stroke_color(self, color: Color):
"""Set stroke color."""
r, g, b = color.red, color.green, color.blue
self._cs.set_stroke_color(r, g, b)
return self
def fill_color(self, color):
def fill_color(self, color: Color):
"""Set fill color."""
r, g, b = color.red, color.green, color.blue
self._cs.set_fill_color(r, g, b)
return self
def line_width(self, width):
"""Set line width."""
self._cs.set_line_width(width)
return self
def line(self, x1, y1, x2, y2):
"""Draw line from (x1,y1) to (x2,y2)."""
self._cs.line(x1, y1, x2, y2)
self._cs.stroke_and_close()
return self
def rect(self, x, y, w, h, fill):
"""Draw optionally filled rectangle at (x,y) with width w and height h."""
self._cs.append_rectangle(x, y, w, h)
if fill:
self._cs.fill()
@@ -309,7 +325,8 @@ class PikepdfCanvasAccessor:
return self
def draw_image(self, image: Path | str | Image.Image, x, y, width, height):
with self.enter_context():
"""Draw image at (x,y) with width w and height h."""
with self.save_state():
self.cm(Matrix(width, 0, 0, height, x, y))
if isinstance(image, (Path, str)):
image = Image.open(image)
@@ -322,59 +339,71 @@ class PikepdfCanvasAccessor:
li = LoadedImage(name, image)
self._images.append(li)
self._cs.draw_form_xobject(name)
return self
def draw_text(self, text: PikepdfText):
self._cs._instructions.extend(text._cs.build())
self._end_text()
def _end_text(self):
"""Draw text object."""
self._cs.extend(text._cs)
self._cs.end_text()
return self
def dashes(self, *args):
"""Set dashes."""
self._cs.set_dashes(*args)
return self
def push(self):
"""Save the graphics state."""
self._cs.push()
self._stack_depth += 1
return self
def pop(self):
"""Restore the graphics state."""
self._cs.pop()
self._stack_depth -= 1
return self
@contextmanager
def enter_context(self):
def save_state(self):
"""Save the graphics state and restore it on exit."""
self.push()
yield self
self.pop()
def cm(self, matrix):
def cm(self, matrix: Matrix):
"""Concatenate a new transformation matrix to the current matrix."""
self._cs.cm(matrix)
return self
class PikepdfCanvas:
"""Canvas for rendering PDFs with pikepdf.
All drawing is done on a pikepdf canvas using the .do property.
This interface manages the graphics state of the canvas and saves it.
"""
def __init__(self, *, page_size: tuple[int | float, int | float]):
self.page_size = page_size
self._pdf = Pdf.new()
self._page = self._pdf.add_blank_page(page_size=page_size)
self._cs = ContentStreamBuilder()
self._images: list[LoadedImage] = []
self._accessor = PikepdfCanvasAccessor(self._cs, self._images)
self._accessor = _PikepdfCanvasAccessor(self._cs, self._images)
self._stack_depth = 0
self._font_name = Name("/f-0-0")
self.do.push()
@property
def do(self) -> PikepdfCanvasAccessor:
def do(self) -> _PikepdfCanvasAccessor:
"""Do operations on the current graphics state."""
return self._accessor
def string_width(self, text, fontname, fontsize):
def string_width(self, s: str, fontname, fontsize):
"""Estimate the width of a text string when rendered with the given font."""
# NFKC: split ligatures, combine diacritics
return len(unicodedata.normalize("NFKC", text)) * (fontsize / CHAR_ASPECT)
return len(unicodedata.normalize("NFKC", s)) * (fontsize / CHAR_ASPECT)
def _save_image(self, li: LoadedImage):
return self._pdf.make_stream(
@@ -390,15 +419,14 @@ class PikepdfCanvas:
)
def save(self, output_file: Path):
"""Save the page to the output file."""
self.do.pop()
if self._stack_depth != 0:
log.warning(
"Graphics state stack is not empty when page saved - "
"rendering may be incorrect"
)
self._page.Contents = self._pdf.make_stream(
unparse_content_stream(self._cs.build())
)
self._page.Contents = self._pdf.make_stream(self._cs.build())
self._page.MediaBox = [0, 0, *self.page_size]
self._page.Resources = Dictionary(Font=Dictionary(), XObject=Dictionary())
self._page.Resources.Font[self._font_name] = register_glyphlessfont(self._pdf)
@@ -408,6 +436,8 @@ class PikepdfCanvas:
class PikepdfText:
"""Text object for rendering text on a pikepdf canvas."""
def __init__(self, x=0, y=0, direction=TextDirection.LTR):
self._cs = ContentStreamBuilder()
self._cs.begin_text()
src/ocrmypdf/hocrtransform/_hocr.py
+8 -8
View File
@@ -170,7 +170,7 @@ class HocrTransform:
# create the PDF file
# page size in points (1/72 in.)
canvas = Canvas(page_size=(self.width, self.height))
with canvas.do.enter_context():
with canvas.do.save_state():
page_matrix = (
Matrix()
.translated(0, self.height)
@@ -260,7 +260,7 @@ class HocrTransform:
# Setup a new coordinate system on the line box's intercept and rotated by
# its slope.
with canvas.do.enter_context():
with canvas.do.save_state():
line_matrix = (
Matrix()
.translated(*bottom_left_corner)
@@ -362,7 +362,7 @@ class HocrTransform:
"""Draw boxes around paragraphs in the document."""
if not self.render_options.render_paragraph_bbox: # pragma: no cover
return
with canvas.do.enter_context():
with canvas.do.save_state():
# draw box around paragraph
canvas.do.stroke_color(color).line_width(0.1)
for elem in self.hocr.iterfind(self._child_xpath('p', 'ocr_par')):
@@ -380,7 +380,7 @@ class HocrTransform:
"""Render the bounding box of a text line."""
if not self.render_options.render_line_bbox: # pragma: no cover
return
with canvas.do.enter_context():
with canvas.do.save_state():
canvas.do.stroke_color(color).line_width(0.15).rect(
line_box.llx, line_box.lly, line_box.width, line_box.height, fill=0
)
@@ -391,7 +391,7 @@ class HocrTransform:
"""Render a triangle that conveys word height and drawing direction."""
if not self.render_options.render_triangle: # pragma: no cover
return
with canvas.do.enter_context():
with canvas.do.save_state():
canvas.do.stroke_color(color).line_width(line_width).line(
box.llx, box.lly, box.urx, box.lly
).line(box.urx, box.lly, box.llx, box.ury).line(
@@ -404,7 +404,7 @@ class HocrTransform:
"""Render a box depicting the word."""
if not self.render_options.render_word_bbox: # pragma: no cover
return
with canvas.do.enter_context():
with canvas.do.save_state():
canvas.do.stroke_color(color).line_width(line_width).rect(
box.llx, box.lly, box.width, box.height, fill=0
)
@@ -415,7 +415,7 @@ class HocrTransform:
"""Render a box depicting the space between two words."""
if not self.render_options.render_space_bbox: # pragma: no cover
return
with canvas.do.enter_context():
with canvas.do.save_state():
canvas.do.fill_color(color).line_width(line_width).rect(
box.llx, box.lly, box.width, box.height, fill=1
)
@@ -431,7 +431,7 @@ class HocrTransform:
"""Render the text baseline."""
if not self.render_options.render_baseline:
return
with canvas.do.enter_context():
with canvas.do.save_state():
canvas.do.stroke_color(color).line_width(line_width).line(
line_box.llx,
baseline_lly,