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feat(reader): add PDF reading support with outline chapters, CLI blocks, and noise filtering (task 7)

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Antigravity committed 2026-10-06 10:16:40 +03:00
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app/vendor/pypdf/generic/_appearance_stream.py
Vendored
+894
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from __future__ import annotations
import copy
import re
from dataclasses import dataclass, field
from enum import IntEnum
from io import BytesIO
from operator import attrgetter
from typing import TYPE_CHECKING, Any, NamedTuple, cast
from .._codecs import encoding_dict_from_named_encoding
from .._codecs.core_font_metrics import CORE_FONT_METRICS
from .._font import Font
from .._page import Transformation
from .._utils import is_char_rtl, logger_warning
from ..constants import AnnotationDictionaryAttributes, BorderStyles, FieldDictionaryAttributes, PageAttributes
from ..errors import PdfReadError
from ..generic import (
ArrayObject,
DecodedStreamObject,
DictionaryObject,
FloatObject,
IndirectObject,
NameObject,
NumberObject,
RectangleObject,
StreamObject,
)
from ..generic._base import ByteStringObject, TextStringObject
from ._color import Color, DeviceGray
if TYPE_CHECKING:
from pypdf._writer import PdfWriter
from .._page import PageObject
try:
import arabic_reshaper
from bidi.algorithm import get_display
HAS_RTL_SUPPORT = True
except ImportError:
HAS_RTL_SUPPORT = False
DEFAULT_FONT_SIZE_IN_MULTILINE = 12
# "The glyph widths shall be measured in units in which 1000 units correspond to 1 unit in text space"
# (Table 111, PDF Specification 2.0)
TEXT_SPACE_TO_GLYPH_SPACE_FACTOR = 1000
@dataclass
class BaseStreamConfig:
"""A container representing the basic layout of an appearance stream."""
rectangle: RectangleObject = field(default_factory=lambda: RectangleObject((0.0, 0.0, 0.0, 0.0)))
border_width: int = 1 # The width of the border in points
border_style: str = BorderStyles.SOLID
border_color: Color | None = None
background_color: Color | None = None
rotation: int = 0
class BaseStreamAppearance(DecodedStreamObject):
"""A class representing the very base of an appearance stream, that is, a rectangle and a border."""
def _add_matrix(self, rotation: int) -> None:
# We need to rotate our rectangle while keeping its origin to (0, 0).
# Rotation goes counterclockwise. We want to know the furthest points to which we rotated left and down.
# These will serve as our X and Y offsets to translate the entire object origin back to (0, 0).
# If a corner rotates into negative space, that is our offset. If none does, the minimum is 0.0.
matrix = Transformation().rotate(rotation)
bottom_right_corner = (self._layout.rectangle.width, 0.0)
top_left_corner = (0.0, self._layout.rectangle.height)
top_right_corner = (self._layout.rectangle.width, self._layout.rectangle.height)
rotated_bottom_right_corner = matrix.apply_on(bottom_right_corner)
rotated_top_left_corner = matrix.apply_on(top_left_corner)
rotated_top_right_corner = matrix.apply_on(top_right_corner)
translation_x_offset = -min(
0.0, rotated_bottom_right_corner[0], rotated_top_left_corner[0], rotated_top_right_corner[0]
)
translation_y_offset = -min(
0.0, rotated_bottom_right_corner[1], rotated_top_left_corner[1], rotated_top_right_corner[1]
)
matrix = matrix.translate(translation_x_offset, translation_y_offset)
self[NameObject("/Matrix")] = ArrayObject([FloatObject(round(i, 3)) for i in matrix.ctm])
def __init__(self, layout: BaseStreamConfig | None) -> None:
"""
Takes the appearance stream layout as an argument.
Args:
layout: The basic layout parameters.
"""
super().__init__()
self._layout = layout or BaseStreamConfig()
self[NameObject("/Type")] = NameObject("/XObject")
self[NameObject("/Subtype")] = NameObject("/Form")
self[NameObject("/BBox")] = self._layout.rectangle
# Define the rotation matrix
rotation = self._layout.rotation % 360
if rotation:
self._add_matrix(rotation)
ap_stream_parts = []
# Only add a background color when color is defined and not transparent
if isinstance(self._layout.background_color, Color):
ap_stream_parts.append(
f"0 0 {self._layout.rectangle.width} {self._layout.rectangle.height} re\n"
f"{self._layout.background_color.as_operator()}\n"
"f\n"
)
# Only add a border when border width is larger than 0, border
# color is defined, and border color is not set to transparent.
if self._layout.border_width > 0:
if isinstance(self._layout.border_color, Color):
border_width_string = f"{self._layout.border_width} w\n" if self._layout.border_width != 1 else ""
ap_stream_parts.append(
f"{self._layout.border_width} "
f"{self._layout.border_width} "
f"{self._layout.rectangle.width - 2 * self._layout.border_width} "
f"{self._layout.rectangle.height - 2 * self._layout.border_width} re\n"
f"{border_width_string}"
f"{self._layout.border_color.as_operator(stroke=True)}\n"
"s\n"
)
else:
# If we aren't drawing a border, then set border_width to 0. This means less margin to
# take into account and results in larger font sizes.
self._layout.border_width = 0
if ap_stream_parts:
ap_stream_parts.insert(0, "q\n")
ap_stream_parts.append("Q\n")
self._ap_stream_data = "".join(ap_stream_parts).encode()
class TextAlignment(IntEnum):
"""Defines the alignment options for text within a form field's appearance stream."""
LEFT = 0
CENTER = 1
RIGHT = 2
class WidthWordGlyphs(NamedTuple):
"""A tuple of the unscaled width of a word (unencoded text) and the font-encoded glyphs that represent it."""
width: float
word: str
glyphs: str
class TextStreamAppearance(BaseStreamAppearance):
"""
A class representing the appearance stream for a text-based form field.
This class generates the content stream (the `ap_stream_data`) that dictates
how text is rendered within a form field's bounding box. It handles properties
like font, font size, color, multiline text, and text selection highlighting.
"""
def _scale_text(
self,
font: Font,
font_size: float,
leading_factor: float,
field_width: float,
field_height: float,
paragraphs: list[list[WidthWordGlyphs]],
min_font_size: float,
font_size_step: float = 0.2
) -> tuple[list[WidthWordGlyphs], float]:
"""
Takes a piece of text and scales it to field_width or field_height, given font_name
and font_size. Wraps text where necessary.
Args:
font: The font to be used.
font_size: The font size in points.
leading_factor: The line distance.
field_width: The width of the field in which to fit the text.
field_height: The height of the field in which to fit the text.
paragraphs: The list of text paragraphs to fit with the field, where each paragraph is a list
of tuples of unscaled width, unencoded text, and glyphs (font-encoded text).
min_font_size: The minimum font size at which to scale the text.
font_size_step: The amount by which to decrement font size per step while scaling.
Returns:
The text in the form of list of tuples, each tuple containing the length of a line
and its contents, and the font_size for these lines and lengths.
"""
wrapped_lines = []
current_line_words: list[WidthWordGlyphs] = []
current_line_width: float = 0
space_width = font.space_width * font_size / TEXT_SPACE_TO_GLYPH_SPACE_FACTOR
for paragraph in paragraphs:
for i, width_word_glyphs in enumerate(paragraph):
word_width = width_word_glyphs.width * font_size
test_width = current_line_width + word_width + (space_width if i else 0)
if test_width > field_width and current_line_words:
wrapped_lines.append(
WidthWordGlyphs(
width=current_line_width,
word=" ".join(map(attrgetter("word"), current_line_words)),
glyphs=font.space_char.join(map(attrgetter("glyphs"), current_line_words))
)
)
current_line_words = [width_word_glyphs]
current_line_width = word_width
elif not current_line_words and word_width > field_width:
wrapped_lines.append(
WidthWordGlyphs(
width=word_width,
word=width_word_glyphs.word,
glyphs=width_word_glyphs.glyphs
)
)
current_line_words = []
current_line_width = 0
else:
if current_line_words:
current_line_width += space_width
current_line_words.append(width_word_glyphs)
current_line_width += word_width
if current_line_words:
wrapped_lines.append(WidthWordGlyphs(
width=current_line_width,
word=" ".join(map(attrgetter("word"), current_line_words)),
glyphs=font.space_char.join(map(attrgetter("glyphs"), current_line_words))
))
current_line_words = []
current_line_width = 0
# Estimate total height.
estimated_total_height = font_size + (len(wrapped_lines) - 1) * leading_factor * font_size
if estimated_total_height > field_height:
# Text overflows height; Retry with smaller font size.
new_font_size = font_size - font_size_step
if new_font_size >= min_font_size:
return self._scale_text(
font,
new_font_size,
leading_factor,
field_width,
field_height,
paragraphs,
min_font_size,
font_size_step
)
return wrapped_lines, round(font_size, 1)
def _generate_appearance_stream_data(
self,
text: str,
selection: list[str] | None ,
font: Font,
font_name: str = "/Helv",
font_size: float = 0.0,
font_color: Color | None = None,
is_multiline: bool = False,
alignment: TextAlignment = TextAlignment.LEFT,
is_comb: bool = False,
max_length: int | None = None
) -> bytes:
"""
Generates the raw bytes of the PDF appearance stream for a text field.
This private method assembles the PDF content stream operators to draw
the provided text within the specified rectangle. It handles text positioning,
font application, color, and special formatting like selected text.
Args:
text: The text to be rendered in the form field.
selection: An optional list of strings that should be highlighted as selected.
font: The font to use.
font_name: The name of the font resource to use (e.g., "/Helv").
font_size: The font size. If 0, it is automatically calculated
based on whether the field is multiline or not.
font_color: The color to apply to the font, represented as a class Color
is_multiline: A boolean indicating if the text field is multiline.
alignment: Text alignment, can be TextAlignment.LEFT, .RIGHT, or .CENTER.
is_comb: Boolean that designates fixed-length fields, where every character
fills one "cell", such as in a postcode.
max_length: Used if is_comb is set. The maximum number of characters for a fixed-
length field.
Returns:
A byte string containing the PDF content stream data.
"""
font_color = font_color or DeviceGray()
rectangle = self._layout.rectangle
leading_factor = (
(font.font_descriptor.bbox[3] - font.font_descriptor.bbox[1]) / TEXT_SPACE_TO_GLYPH_SPACE_FACTOR
)
# Set margins based on border width and style
factor = 2 if self._layout.border_style in {"/B", "/I"} else 1
margin = self._layout.border_width * factor
field_height = rectangle.height - 2 * margin
field_width = rectangle.width - 4 * max(margin, 1)
reverse_cmap, encoding_cmap = font._get_typographic_maps()
def _unicode_to_glyph_id(text: str, reverse_cmap: dict[str, str]) -> str:
if HAS_RTL_SUPPORT:
# Use arabic-reshaper and python-bidi to rearrange and shape text for the PDF engine
reshaped_text = arabic_reshaper.reshape(text)
visual_text = get_display(reshaped_text, base_dir="L")
return "".join(reverse_cmap.get(char, char) for char in visual_text)
return "".join(reverse_cmap.get(char, char) for char in text)
def _glyph_id_to_bytes(glyphs: str, encoding_cmap: dict[str, bytes]) -> list[bytes]:
return [encoding_cmap.get(
glyph_id, bytes((ord(glyph_id),)) if ord(glyph_id) < 256 else b"?"
) for glyph_id in glyphs]
# If font_size is 0, apply the logic for multiline or large-as-possible font
if font_size == 0:
min_font_size = 4.0 # The minimum font size
if selection: # Don't wrap text when dealing with a /Ch field, in order to prevent problems
is_multiline = False # with matching "selection" with "line" later on.
if is_multiline:
font_size = DEFAULT_FONT_SIZE_IN_MULTILINE
# We create a list of paragraphs, here each paragraph is a list of tuples, where each WidthWordGlyphs
# tuple signifies an unscaled word width, the word itself, and the glyphs that encode it.
paragraphs: list[list[WidthWordGlyphs]] = []
for line in text.splitlines():
if not line.strip():
paragraphs.append([WidthWordGlyphs(width=0.0, word="", glyphs="")])
continue
line_by_widths_words_glyphs: list[WidthWordGlyphs] = []
words = line.split(" ")
for word in words:
glyph_word = _unicode_to_glyph_id(word, reverse_cmap)
line_by_widths_words_glyphs.append(
WidthWordGlyphs(
width=font.get_text_width(word) / TEXT_SPACE_TO_GLYPH_SPACE_FACTOR,
word=word,
glyphs=glyph_word
)
)
paragraphs.append(line_by_widths_words_glyphs)
lines, font_size = self._scale_text(
font,
font_size,
leading_factor,
field_width,
field_height,
paragraphs,
min_font_size
)
else:
max_vertical_size = field_height / leading_factor
glyphs = _unicode_to_glyph_id(text, reverse_cmap)
text_width_unscaled = font.get_text_width(glyphs) / TEXT_SPACE_TO_GLYPH_SPACE_FACTOR
max_horizontal_size = field_width / (text_width_unscaled or 1)
font_size = round(max(min(max_vertical_size, max_horizontal_size), min_font_size), 1)
lines = [WidthWordGlyphs(width=text_width_unscaled * font_size, word=text, glyphs=glyphs)]
elif is_comb:
if max_length and len(text) > max_length:
logger_warning(
(
"Length of text %(text)s exceeds maximum length (%(max_length)d) "
"of field, input truncated."
),
source=__name__,
text=text,
max_length=max_length,
)
# We act as if each character is one line, because we draw it separately later on
lines = []
for index, char in enumerate(text):
if index < (max_length or len(text)):
glyphs = _unicode_to_glyph_id(char, reverse_cmap)
lines.append(
WidthWordGlyphs(
width=font.get_text_width(glyphs) * font_size / TEXT_SPACE_TO_GLYPH_SPACE_FACTOR,
word=char,
glyphs=glyphs
)
)
else:
lines = []
for line in text.splitlines():
glyphs = _unicode_to_glyph_id(line, reverse_cmap)
lines.append(
WidthWordGlyphs(
width=font.get_text_width(glyphs) * font_size / TEXT_SPACE_TO_GLYPH_SPACE_FACTOR,
word=line,
glyphs=glyphs
)
)
# Set the vertical offset
if is_multiline:
y_offset = (
field_height + margin - font.font_descriptor.bbox[3] * font_size / TEXT_SPACE_TO_GLYPH_SPACE_FACTOR
)
else:
y_offset = margin + (
(field_height - font.font_descriptor.ascent * font_size / TEXT_SPACE_TO_GLYPH_SPACE_FACTOR) / 2
)
default_appearance = f"{font_name} {font_size} Tf {font_color.as_operator()}"
ap_stream = bytearray()
ap_stream += (
f"q\n/Tx BMC \nq\n"
f"{2 * max(margin, 1)} {margin} "
f"{round(field_width - 2 * max(margin, 1), 3)} {round(field_height - margin, 3)} re\n"
f"W\nBT\n{default_appearance}\n"
).encode()
current_x_pos: float = 0 # Initial virtual position within the text object.
selection_glyphs = _unicode_to_glyph_id("".join(selection), reverse_cmap) if selection else ""
for line_number, (line_width, original_text, line) in enumerate(lines):
if selection_glyphs and line in selection_glyphs:
# Might be improved, but cannot find how to get fill working => replaced with lined box
ap_stream += (
f"1 {round(y_offset - (line_number * font_size * leading_factor) - 1, 3)} "
f"{rectangle.width - 2} {font_size + 2} re\n"
f"0.5 0.5 0.5 rg s\n{default_appearance}\n"
).encode()
# Calculate the desired absolute starting X for the current line
desired_abs_x_start: float = 0
if is_comb and max_length:
# Calculate the width of a cell for one character
cell_width = rectangle.width / max_length
# Space from the left edge of the cell to the character's baseline start
# line_width here is the *actual* character width in points for the single character 'line'
centering_offset_in_cell = (cell_width - line_width) / 2
# Absolute start X = (Cell Index, i.e., line_number * Cell Width) + Centering Offset
desired_abs_x_start = (line_number * cell_width) + centering_offset_in_cell
elif alignment == TextAlignment.RIGHT:
desired_abs_x_start = rectangle.width - max(margin, 1) * 2 - line_width
elif alignment == TextAlignment.CENTER:
desired_abs_x_start = (rectangle.width - line_width) / 2
else: # Left aligned; default
desired_abs_x_start = max(margin, 1) * 2
# Calculate x_rel_offset: how much to move from the current_x_pos
# to reach the desired_abs_x_start.
x_rel_offset = desired_abs_x_start - current_x_pos
# Y-offset:
y_rel_offset: float = 0
if line_number == 0:
y_rel_offset = y_offset # Initial vertical position
elif is_comb:
y_rel_offset = 0.0 # DO NOT move vertically for subsequent characters
else:
y_rel_offset = - font_size * leading_factor # Move down by line height
# Td is a relative translation (Tx and Ty).
# It updates the current text position.
ap_stream += f"{round(x_rel_offset, 3)} {round(y_rel_offset, 3)} Td\n".encode()
# Update current_x_pos based on the Td operation for the next iteration.
# This is the X position where the *current line* will start.
current_x_pos = desired_abs_x_start
is_rtl = any(is_char_rtl(char) for char in line)
encoded_line = _glyph_id_to_bytes(line, encoding_cmap)
if is_rtl:
# Encode input text as UTF-16BE with a BOM, so that the input text is returned
# in the right direction when copying text from the resulting PDF
bom_text = b"\xfe\xff" + original_text.encode("utf-16-be")
hex_original_text = bom_text.hex().upper()
ap_stream += f"/Span << /ActualText <{hex_original_text}> >> BDC\n".encode()
if font.sub_type == "Type0": # 16-bit font
ap_stream += b"<" + (b"".join(encoded_line)).hex().encode() + b"> Tj\n"
else: # Simple font, 8-bit encoded.
# Escape parentheses (PDF 1.7 reference, table 3.2, Literal Strings)
line_as_bytes = (
b"".join(encoded_line)
.replace(b"\\", b"\\\\")
.replace(b"(", br"\(")
.replace(b")", br"\)")
)
ap_stream += b"(" + line_as_bytes + b") Tj\n"
if is_rtl:
ap_stream += b"EMC\n"
ap_stream += b"ET\nQ\nEMC\nQ\n"
return bytes(ap_stream)
def __init__(
self,
layout: BaseStreamConfig | None = None,
text: str = "",
selection: list[str] | None = None,
font: Font | None = None,
font_resource: DictionaryObject | IndirectObject | None = None,
font_name: str = "/Helv",
font_size: float = 0.0,
font_color: Color | None = None,
is_multiline: bool = False,
alignment: TextAlignment = TextAlignment.LEFT,
is_comb: bool = False,
max_length: int | None = None
) -> None:
"""
Initializes a TextStreamAppearance object.
This constructor creates a new PDF stream object configured as an XObject
of subtype Form. It uses the `_generate_appearance_stream_data` method to
generate the content for the stream.
Args:
layout: The basic layout parameters.
text: The text to be rendered in the form field.
selection: An optional list of strings that should be highlighted as selected.
font: A Font object. Falls back to Type 1 Helvetica if not given.
font_resource: An optional variable that represents a PDF font dictionary. Falls back
to Type 1 Helvetica if not given.
font_name: The name of the font resource, e.g., "/Helv".
font_size: The font size. If 0, it's auto-calculated.
font_color: The font color string.
is_multiline: A boolean indicating if the text field is multiline.
alignment: Text alignment, can be TextAlignment.LEFT, .RIGHT, or .CENTER.
is_comb: Boolean that designates fixed-length fields, where every character
fills one "cell", such as in a postcode.
max_length: Used if is_comb is set. The maximum number of characters for a fixed-
length field.
"""
super().__init__(layout)
if not font or not font_resource:
font_name = "/Helv"
font = Font.from_core_font_name()
font_resource = font.as_font_resource()
self._ap_stream_data += self._generate_appearance_stream_data(
text,
selection,
font,
font_name=font_name,
font_size=font_size,
font_color=font_color or DeviceGray(),
is_multiline=is_multiline,
alignment=alignment,
is_comb=is_comb,
max_length=max_length
)
self.set_data(ByteStringObject(self._ap_stream_data))
self[NameObject("/Length")] = NumberObject(len(self._ap_stream_data))
# Update Resources with font information
self[NameObject("/Resources")] = DictionaryObject({
NameObject("/Font"): DictionaryObject({
NameObject(font_name): getattr(font_resource, "indirect_reference", font_resource)
})
})
@staticmethod
def _find_annotation_font_resource(
font_name: str,
annotation: DictionaryObject,
acro_form: DictionaryObject,
text: str
) -> tuple[str, Font]:
# Try to find a resource dictionary for the font by examining the annotation and, if that fails,
# the AcroForm resources dictionary
acro_form_resources: Any = cast(
DictionaryObject,
annotation.get_inherited(
"/DR",
acro_form.get("/DR", DictionaryObject()),
),
)
acro_form_font_resources = acro_form_resources.get("/Font", DictionaryObject())
font_resource = acro_form_font_resources.get(font_name, None)
if font_resource:
font = Font.from_font_resource(font_resource.get_object())
else:
# Normally, we should have found a font resource by now. However, when a user has provided a specific
# font name, we may not have found the associated font resource among the AcroForm resources. Also, in
# case of the 14 Adobe Core fonts, we may be expected to construct a font resource ourselves.
if font_name.removeprefix("/") not in CORE_FONT_METRICS:
# Default to Helvetica if we haven't found a font resource and cannot construct one ourselves.
logger_warning(
"Font dictionary for %(font_name)s not found; defaulting to Helvetica.",
source=__name__,
font_name=font_name,
)
font_name = "/Helvetica"
font = Font.from_core_font_name(font_name)
# If we have found a font resource, it still might not be able to encode the text value we received.
encodable = font.can_encode(text)
if not encodable:
# If we have a font file, we can try to produce a new font resource with an encoding
# that does include the necessary characters. We only try this for a TrueType font, meaning
# that, in PDF terms, it is a simple, 8-bit encoded font.
if font.font_descriptor.font_file and font.sub_type == "TrueType":
try:
font = font.from_truetype_font_file(BytesIO(font.font_descriptor.font_file.get_data()))
font_name = "/PYPDF1" # This means we most probably do not clash with an existing font name
encodable = font.can_encode(text)
except (ImportError, PdfReadError) as e:
logger_warning("Unable to use embedded font for encoding: %(e)s", source=__name__, e=e)
# If it's one of the unembedded 14 Adobe Core Fonts, we can test other supported encodings
elif font.sub_type == "Type1" and font.name in CORE_FONT_METRICS:
core_font_metrics = CORE_FONT_METRICS[font.name]
test_encodings = {
"cp1250", # Central / Eastern European
"cp1252", # Western European
"cp1254", # Turkish
"cp1257", # Baltic Rim
"iso8859_15" # Western European ISO Alternate
}
for encoding in test_encodings:
test_font = copy.copy(font)
test_font.encoding = encoding_dict_from_named_encoding(encoding)
encodable = test_font.can_encode(text)
if encodable:
font = test_font
font.character_widths.clear()
for code, character in test_font.encoding.items():
# Look up the width using the glyph name from the encoding
if character in core_font_metrics.character_widths:
font.character_widths[chr(code)] = core_font_metrics.character_widths[character]
font.character_widths["default"] = core_font_metrics.character_widths["default"]
font_name = "/PYPDF1" + encoding
break
if not encodable:
logger_warning(
(
"Text string '%(text)s' contains characters not supported by font encoding. "
"This may result in text corruption. "
"Consider calling writer.update_page_form_field_values with auto_regenerate=True."
),
source=__name__,
text=text,
)
return font_name, font
@staticmethod
def _sync_appearance_stream_font_resources(
writer: PdfWriter,
font_name: str,
font: Font,
target_resource_dict: DictionaryObject,
page: PageObject | None = None
) -> IndirectObject:
"""
Unified helper to sync fonts from an AP stream to a target resource dictionary (e.g., AcroForm /DR).
Will sync to page resources as well when page is added to the arguments.
"""
target_fonts = target_resource_dict.setdefault(NameObject("/Font"), DictionaryObject()).get_object()
if font_name not in target_fonts:
font_resource_reference = font._add_to_writer(
writer,
target_fonts,
NameObject(font_name)
)
else:
font_resource_reference = target_fonts[font_name]
if page:
page_fonts_resource = cast(DictionaryObject, page[PageAttributes.RESOURCES]).setdefault(
NameObject("/Font"), DictionaryObject()
).get_object()
if font_name not in page_fonts_resource:
page_fonts_resource[NameObject(font_name)] = getattr(
font_resource_reference, "indirect_reference", font_resource_reference
)
return font_resource_reference
@classmethod
def from_text_annotation(
cls,
writer: PdfWriter,
page: PageObject,
flatten: bool,
acro_form: DictionaryObject, # _root_object[CatalogAttributes.ACRO_FORM])
field: DictionaryObject,
annotation: DictionaryObject,
user_font_name: str = "",
user_font_size: float = -1,
) -> TextStreamAppearance:
"""
Creates a TextStreamAppearance object from a text field annotation.
This class method is a factory for creating a `TextStreamAppearance`
instance by extracting all necessary information (bounding box, font,
text content, etc.) from the PDF field and annotation dictionaries.
It respects inheritance for properties like default appearance (`/DA`).
Args:
writer: The PdfWriter instance that we are creating text stream appearances for.
page: The page that we are processing annotations for.
flatten: Whether we flatten text annotations or not. If true, add new font resource
to the page font resources. Otherwise, add them to the AcroForm resources.
acro_form: The root AcroForm dictionary from the PDF catalog.
field: The field dictionary object.
annotation: The widget annotation dictionary object associated with the field.
user_font_name: An optional user-provided font name to override the
default. Defaults to an empty string.
user_font_size: An optional user-provided font size to override the
default. A value of -1 indicates no override.
Returns:
A new `TextStreamAppearance` instance configured for the given field.
"""
# Calculate rectangle dimensions
_rectangle = cast(RectangleObject, annotation[AnnotationDictionaryAttributes.Rect])
# Normalize the rectangle, apply page rotation if applicable
if page.get_inherited("/Rotate") in {90, 270}:
rectangle = RectangleObject((0, 0, abs(_rectangle[3] - _rectangle[1]), abs(_rectangle[2] - _rectangle[0])))
else:
rectangle = RectangleObject((0, 0, abs(_rectangle[2] - _rectangle[0]), abs(_rectangle[3] - _rectangle[1])))
# Get default appearance dictionary from annotation
default_appearance = annotation.get_inherited(
AnnotationDictionaryAttributes.DA,
acro_form.get(AnnotationDictionaryAttributes.DA, None),
)
if not default_appearance:
# Create a default appearance if none was found in the annotation
default_appearance = TextStringObject("/Helv 0 Tf 0 g")
else:
default_appearance = default_appearance.get_object()
# Retrieve field text and selected values
field_flags = field.get(FieldDictionaryAttributes.Ff, 0)
if (
field.get(FieldDictionaryAttributes.FT, "/Tx") == "/Ch" and
field_flags & FieldDictionaryAttributes.FfBits.Combo == 0
):
text = "\n".join(annotation.get_inherited(FieldDictionaryAttributes.Opt, []))
selection = field.get("/V", [])
if not isinstance(selection, list):
selection = [selection]
else: # /Tx
text = field.get("/V", "")
selection = []
# Derive font name, size and color from the default appearance. Also set
# user-provided font name and font size in the default appearance, if given.
# For a font name, this presumes that we can find an associated font resource
# dictionary. Uses the variable font_properties as an intermediate.
# As per the PDF spec:
# "At a minimum, the string [that is, default_appearance] shall include a Tf (text
# font) operator along with its two operands, font and size" (Section 12.7.4.3
# "Variable text" of the PDF 2.0 specification).
font_properties = [prop for prop in re.split(r"\s", default_appearance) if prop]
da_font_name = font_properties.pop(font_properties.index("Tf") - 2)
font_size = float(font_properties.pop(font_properties.index("Tf") - 1))
font_properties.remove("Tf")
font_color = Color.from_normalized_values(tuple(float(val) for val in font_properties[:-1]))
# Determine the font name to use, prioritizing the user's input
if user_font_name:
font_name = user_font_name
else:
font_name = da_font_name
# Determine the font size to use, prioritizing the user's input
if user_font_size > 0:
font_size = user_font_size
font_name, font = cls._find_annotation_font_resource(font_name, annotation, acro_form, text)
# Change the /DA information if we changed the font name
if font_name != da_font_name:
annotation[NameObject("/DA")] = TextStringObject(default_appearance.replace(da_font_name, font_name))
# Synchronise font resources
font_resource_reference = cls._sync_appearance_stream_font_resources(
writer,
font_name,
font,
acro_form.setdefault(NameObject("/DR"), DictionaryObject()),
page if flatten else None,
)
# Retrieve formatting information
is_comb = False
max_length = None
if field_flags & FieldDictionaryAttributes.FfBits.Comb:
is_comb = True
max_length = annotation.get("/MaxLen")
is_multiline = False
if field_flags & FieldDictionaryAttributes.FfBits.Multiline:
is_multiline = True
alignment = field.get("/Q", TextAlignment.LEFT)
border_width = 1
border_style = BorderStyles.SOLID
if "/BS" in field:
border_width = cast(DictionaryObject, field["/BS"]).get("/W", border_width)
border_style = cast(DictionaryObject, field["/BS"]).get("/S", border_style)
rotation = 0
border_color: Color | None = None
background_color: Color | None = None
appearance_characteristics = field.get_inherited("/MK", None)
if isinstance(appearance_characteristics, DictionaryObject):
rotation = int(appearance_characteristics.get("/R", 0))
# Color.from_normalized_values([]) results in None for a "/BC" or "/BG" value of []
border_color = Color.from_normalized_values(appearance_characteristics.get("/BC"))
background_color = Color.from_normalized_values(appearance_characteristics.get("/BG"))
# Create the TextStreamAppearance instance
layout = BaseStreamConfig(
rectangle=rectangle,
border_width=border_width,
border_style=border_style,
border_color=border_color,
background_color=background_color,
rotation=rotation
)
new_appearance_stream = cls(
layout,
text,
selection,
font,
font_resource_reference,
font_name=font_name,
font_size=font_size,
font_color=font_color,
is_multiline=is_multiline,
alignment=alignment,
is_comb=is_comb,
max_length=max_length
)
if AnnotationDictionaryAttributes.AP in annotation:
for key, value in (
cast(DictionaryObject, annotation[AnnotationDictionaryAttributes.AP]).get("/N", {}).items()
):
if key in {"/BBox", "/Length", "/Subtype", "/Type", "/Filter"}:
continue
# Don't overwrite font resources added by TextAppearanceStream.__init__
if key == "/Resources":
if "/Font" not in value:
value.get_object()[NameObject("/Font")] = DictionaryObject()
value["/Font"].get_object()[NameObject(font_name)] = getattr(
font_resource_reference, "indirect_reference", font_resource_reference
)
else:
new_appearance_stream[key] = value
return new_appearance_stream
def transform_annotation_appearance(annotation_obj: DictionaryObject, transformation: Transformation) -> None:
"""
Compose `transformation` into an annotation's /AP /N appearance stream(s), in place.
Repositioning/resizing an annotation's /Rect alone is not enough: per
the appearance-stream algorithm (PDF 2.0, 12.5.5), a viewer fits the
appearance's /BBox (as mapped by its own /Matrix) into /Rect using an
axis-aligned scale, never a rotation. Left alone, rotating or shearing
a page therefore stretches/skews the untouched appearance content into
the new, differently-shaped /Rect instead of rotating it. Composing the
transform into /Matrix (rather than overwriting it) keeps the rendered
content consistent with the rest of the transformed page while
preserving whatever the annotation already had. Handles both a single
appearance stream and the multi-state /AP /N dict used by
checkbox/radio-button widgets.
"""
if "/AP" not in annotation_obj:
return
ap = cast(DictionaryObject, annotation_obj["/AP"])
if "/N" not in ap:
return
# __getitem__ already resolves indirect references, so this is never None.
normal_ap = ap["/N"]
# /N is a single appearance stream for most annotations, but for
# widgets with multiple states (checkboxes, radio buttons) it is
# instead a dict of named sub-streams, one per state. Only a stream
# carries its own /BBox/Matrix.
state_aps = (
normal_ap.values()
if isinstance(normal_ap, DictionaryObject) and not isinstance(normal_ap, StreamObject)
else [normal_ap]
)
for state_ap in state_aps:
# get_object() is always safe to call: PdfObject.get_object() just
# returns self when the object is already resolved.
state_obj = state_ap.get_object()
if not isinstance(state_obj, StreamObject):
continue
old_matrix = tuple(state_obj.get("/Matrix", (1, 0, 0, 1, 0, 0)))
state_obj[NameObject("/Matrix")] = ArrayObject(
FloatObject(x) for x in Transformation(old_matrix).transform(transformation).ctm
)