Create pikepdf backend renderer
This commit is contained in:
James R. Barlow
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from __future__ import annotations
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import importlib
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import os
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import re
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import unicodedata
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import warnings
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from io import BufferedReader, BufferedWriter, BytesIO
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from pathlib import Path
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import pikepdf
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from bs4 import BeautifulSoup
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from pikepdf import (
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ContentStreamInstruction,
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Dictionary,
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Name,
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Operator,
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Pdf,
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unparse_content_stream,
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)
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from ocrmypdf.hocrtransform.backends._base import Canvas as BaseCanvas
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from ocrmypdf.hocrtransform.backends._base import Text as BaseText
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GLYPHLESS_FONT = importlib.resources.read_binary("ocrmypdf", "pdf.ttf")
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CHAR_ASPECT = 2
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def register_glyphlessfont(pdf: Pdf):
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"""Register the glyphless font.
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Create several data structures in the Pdf to describe the font. While it create
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the data, a reference should be set in at least one page's /Resources dictionary
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to retain the font in the output PDF and ensure it is usable on that page.
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"""
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PLACEHOLDER = Name.Placeholder
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basefont = pdf.make_indirect(
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Dictionary(
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BaseFont=Name.GlyphLessFont,
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DescendantFonts=[PLACEHOLDER],
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Encoding=Name("/Identity-H"),
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Subtype=Name.Type0,
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ToUnicode=PLACEHOLDER,
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Type=Name.Font,
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)
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)
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cid_font_type2 = pdf.make_indirect(
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Dictionary(
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BaseFont=Name.GlyphLessFont,
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CIDToGIDMap=PLACEHOLDER,
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CIDSystemInfo=Dictionary(
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Ordering="Identity",
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Registry="Adobe",
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Supplement=0,
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),
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FontDescriptor=PLACEHOLDER,
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Subtype=Name.CIDFontType2,
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Type=Name.Font,
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DW=1000 // CHAR_ASPECT,
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)
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)
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basefont.DescendantFonts = [cid_font_type2]
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cid_font_type2.CIDToGIDMap = pdf.make_stream(b"\x00\x01" * 65536)
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basefont.ToUnicode = pdf.make_stream(
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b"/CIDInit /ProcSet findresource begin\n"
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b"12 dict begin\n"
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b"begincmap\n"
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b"/CIDSystemInfo\n"
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b"<<\n"
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b" /Registry (Adobe)\n"
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b" /Ordering (UCS)\n"
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b" /Supplement 0\n"
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b">> def\n"
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b"/CMapName /Adobe-Identify-UCS def\n"
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b"/CMapType 2 def\n"
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b"1 begincodespacerange\n"
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b"<0000> <FFFF>\n"
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b"endcodespacerange\n"
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b"1 beginbfrange\n"
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b"<0000> <FFFF> <0000>\n"
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b"endbfrange\n"
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b"endcmap\n"
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b"CMapName currentdict /CMap defineresource pop\n"
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b"end\n"
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b"end\n"
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)
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font_descriptor = pdf.make_indirect(
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Dictionary(
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Ascent=1000,
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CapHeight=1000,
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Descent=-1,
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Flags=5, # Fixed pitch and symbolic
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FontBBox=[0, 0, 1000 // CHAR_ASPECT, 1000],
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FontFile2=PLACEHOLDER,
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FontName=Name.GlyphLessFont,
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ItalicAngle=0,
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StemV=80,
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Type=Name.FontDescriptor,
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)
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)
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font_descriptor.FontFile2 = pdf.make_stream(GLYPHLESS_FONT)
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cid_font_type2.FontDescriptor = font_descriptor
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return basefont
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class ContentStreamBuilder:
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def __init__(self, instructions=None):
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self._instructions: list[ContentStreamInstruction] = instructions or []
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def push(self):
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"""Save the graphics state."""
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inst = ContentStreamInstruction([], Operator("q"))
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self._instructions.append(inst)
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return self
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def pop(self):
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"""Restore the graphics state."""
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inst = ContentStreamInstruction([], Operator("Q"))
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self._instructions.append(inst)
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return self
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def cm(self, a: float, b: float, c: float, d: float, e: float, f: float):
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"""Concatenate matrix."""
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inst = ContentStreamInstruction([a, b, c, d, e, f], Operator("cm"))
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self._instructions.append(inst)
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return self
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def begin_text(self):
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"""Begin text object."""
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inst = ContentStreamInstruction([], Operator("BT"))
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self._instructions.append(inst)
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return self
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def end_text(self):
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"""End text object."""
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inst = ContentStreamInstruction([], Operator("ET"))
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self._instructions.append(inst)
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return self
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def begin_marked_content(self, mctype: Name, mcid: int):
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"""Begin marked content sequence."""
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inst = ContentStreamInstruction(
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[mctype, Dictionary(MCID=mcid)], Operator("BDC")
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)
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self._instructions.append(inst)
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return self
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def end_marked_content(self):
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"""End marked content sequence."""
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inst = ContentStreamInstruction([], Operator("EMC"))
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self._instructions.append(inst)
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return self
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def set_text_font(self, font: Name, size: int):
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"""Set text font and size."""
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inst = ContentStreamInstruction([font, size], Operator("Tf"))
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self._instructions.append(inst)
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return self
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def set_text_matrix(
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self, a: float, b: float, c: float, d: float, e: float, f: float
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):
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"""Set text matrix."""
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inst = ContentStreamInstruction([a, b, c, d, e, f], Operator("Tm"))
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self._instructions.append(inst)
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return self
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def set_text_rendering(self, mode: int):
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"""Set text rendering mode."""
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inst = ContentStreamInstruction([mode], Operator("Tr"))
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self._instructions.append(inst)
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return self
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def set_text_horizontal_scaling(self, scale: float):
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"""Set text horizontal scaling."""
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inst = ContentStreamInstruction([scale], Operator("Tz"))
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self._instructions.append(inst)
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return self
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def show_text(self, text: str):
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"""Show text."""
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inst = ContentStreamInstruction([[text.encode("utf-16be")]], Operator("TJ"))
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self._instructions.append(inst)
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return self
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def move_cursor(self, dx, dy):
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"""Move cursor."""
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inst = ContentStreamInstruction([dx, dy], Operator("Td"))
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self._instructions.append(inst)
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return self
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def stroke_and_close(self):
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"""Stroke and close path."""
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inst = ContentStreamInstruction([], Operator("s"))
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self._instructions.append(inst)
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return self
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def append_rectangle(self, x: float, y: float, w: float, h: float):
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"""Append rectangle to path."""
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inst = ContentStreamInstruction([x, y, w, h], Operator("re"))
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self._instructions.append(inst)
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return self
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def set_stroke_color(self, r: float, g: float, b: float):
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"""Set RGB stroke color."""
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inst = ContentStreamInstruction([r, g, b], Operator("RG"))
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self._instructions.append(inst)
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return self
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def set_fill_color(self, r: float, g: float, b: float):
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"""Set RGB fill color."""
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inst = ContentStreamInstruction([r, g, b], Operator("rg"))
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self._instructions.append(inst)
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return self
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def set_line_width(self, width):
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"""Set line width."""
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inst = ContentStreamInstruction([width], Operator("w"))
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self._instructions.append(inst)
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return self
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def line(self, x1: float, y1: float, x2: float, y2: float):
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"""Draw line."""
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insts = [
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ContentStreamInstruction([x1, y1], Operator("m")),
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ContentStreamInstruction([x2, y2], Operator("l")),
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]
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self._instructions.extend(insts)
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return self
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def set_dashes(self, array=None, phase=0):
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"""Set dashes."""
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if array is None:
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array = []
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if isinstance(array, (int, float)):
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array = (array, phase)
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phase = 0
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inst = ContentStreamInstruction([array, phase], Operator("d"))
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self._instructions.append(inst)
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return self
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def build(self):
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return self._instructions
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class PikepdfCanvas(BaseCanvas):
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def __init__(self, path, *, page_size):
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super().__init__(path, page_size=page_size)
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self._pdf = Pdf.new()
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self._page = self._pdf.add_blank_page(page_size=page_size)
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self._cs = ContentStreamBuilder()
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page_height = page_size[1]
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self._cs.push()
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self._cs.cm(1, 0, 0, -1, 0, page_height)
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self._font_name = Name("/f-0-0")
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def set_stroke_color(self, color):
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r, g, b = color
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self._cs.set_stroke_color(r, g, b)
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def set_fill_color(self, color):
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r, g, b = color
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self._cs.set_fill_color(r, g, b)
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def set_line_width(self, width):
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self._cs.set_line_width(width)
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def line(self, x1, y1, x2, y2):
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self._cs.line(x1, y1, x2, y2)
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def begin_text(self, x=0, y=0, direction=None):
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return PikepdfText(self._cs, x, y, direction)
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def draw_text(self, text):
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self._canvas.drawText(text._text)
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def draw_image(self, image: Path, x, y, width, height):
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raise NotImplementedError()
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def string_width(self, text, fontname, fontsize):
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# NFKC: split ligatures, combine diacritics
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return len(unicodedata.normalize("NFKC", text)) / fontsize * CHAR_ASPECT
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def set_dashes(self, dashes):
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self._cs.set_dashes(*dashes)
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def save(self):
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self._cs.pop()
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self._page.Contents = self._pdf.make_stream(
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unparse_content_stream(self._cs.build())
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)
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self._page.Resources = Dictionary(
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Font=Dictionary({self._font_name: register_glyphlessfont(self._pdf)})
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)
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self._pdf.save(self.path)
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class PikepdfText(BaseText):
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def __init__(self, cs: ContentStreamBuilder, x=0, y=0, direction=None):
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self._cs = cs
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self._cs.begin_text()
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self._p0 = (x, y)
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def set_font(self, font, size):
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self._cs.set_text_font(font, size)
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def set_render_mode(self, mode):
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self._cs.set_text_rendering(mode)
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def set_text_transform(self, a, b, c, d, e, f):
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self._cs.set_text_matrix(a, b, c, d, e, f)
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def show(self, text):
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self._cs.show_text(text)
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def set_horiz_scale(self, scale):
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self._cs.set_text_horizontal_scaling(scale)
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def get_start_of_line(self):
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return self._p0
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def move_cursor(self, x, y):
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# ???
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self._cs.move_cursor(x - self._p0[0], y - self._p0[1])
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