def get_reference(self, object: AnyPDFType,
context: WriteTransformerContext) -> Reference:
"""
This function builds a Reference for the input object
References are re-used whenever possible (hashing is used to detect duplicate objects)
"""
obj_id = id(object)
if obj_id in context.indirect_objects_by_id:
cached_indirect_object: AnyPDFType = context.indirect_objects_by_id[
obj_id]
assert not isinstance(cached_indirect_object, Reference)
return cached_indirect_object.get_reference(
) # type: ignore [union-attr]
# look through existing indirect object hashes
obj_hash: int = self._hash(object)
if obj_hash in context.indirect_objects_by_hash:
for obj in context.indirect_objects_by_hash[obj_hash]:
if obj == object:
ref = obj.get_reference() # type: ignore [union-attr]
assert ref is not None
assert isinstance(ref, Reference)
object.set_reference(ref) # type: ignore [union-attr]
return ref
# generate new object number
existing_obj_numbers = set([
item.get_reference().object_number # type: ignore [union-attr]
for sublist in
[v for k, v in context.indirect_objects_by_hash.items()]
for item in sublist
])
obj_number = len(existing_obj_numbers) + 1
while obj_number in existing_obj_numbers: # type: ignore [union-attr]
obj_number += 1
# build reference
ref = Reference(object_number=obj_number)
object.set_reference(ref) # type: ignore [union-attr]
# insert into context.indirect_objects_by_hash
if obj_hash in context.indirect_objects_by_hash:
context.indirect_objects_by_hash[obj_hash].append(object)
else:
context.indirect_objects_by_hash[obj_hash] = [object]
# insert into context.indirect_objects_by_id
context.indirect_objects_by_id[obj_id] = object
# return
return ref
def _start_object(
self,
object_to_transform: AnyPDFType,
context: Optional[WriteTransformerContext],
):
"""
This function starts a new direct object by writing
its reference number followed by "obj" (e.g. "12 0 obj").
It also does some bookkeeping to ensure the byte offset is stored in the XREF
"""
# get offset position
assert context is not None
assert context.destination is not None
byte_offset = context.destination.tell()
# update offset
ref = object_to_transform.get_reference() # type: ignore [union-attr]
assert ref is not None
assert isinstance(ref, Reference)
ref.byte_offset = byte_offset
# write <object number> <generation number> obj
assert ref.object_number is not None
context.destination.write(
bytes(
"%d %d obj\n" %
(ref.object_number, ref.generation_number or 0),
"latin1",
))
def start_object(
self,
object_to_transform: AnyPDFType,
context: Optional[WriteTransformerContext],
):
# get offset position
assert context is not None
assert context.destination is not None
byte_offset = context.destination.tell()
# update offset
ref = object_to_transform.get_reference() # type: ignore [union-attr]
assert ref is not None
assert isinstance(ref, Reference)
ref.byte_offset = byte_offset
# write <object number> <generation number> obj
assert ref.object_number is not None
context.destination.write(
bytes(
"%d %d obj\n" %
(ref.object_number, ref.generation_number or 0),
"latin1",
))
def transform(
self,
object_to_transform: AnyPDFType,
context: Optional[WriteTransformerContext] = None,
):
"""
This method writes an ET.Element (representing XMP meta information) to a byte stream
"""
assert isinstance(object_to_transform, ET.Element)
assert context is not None
assert context.destination is not None
assert context.destination
# build stream
out_value = Stream()
out_value[Name("Type")] = Name("Metadata")
out_value[Name("Subtype")] = Name("XML")
bts = ET.tostring(object_to_transform)
out_value[Name("DecodedBytes")] = bts
out_value[Name("Bytes")] = bts
out_value[Name("Length")] = pDecimal(len(bts))
# copy reference
out_value.set_reference(
object_to_transform.get_reference()) # type: ignore [attr-defined]
# start object if needed
started_object = False
ref = out_value.get_reference() # type: ignore [attr-defined]
if ref is not None:
assert isinstance(ref, Reference)
if ref.object_number is not None and ref.byte_offset is None:
started_object = True
self.start_object(out_value, context)
# pass stream along to other transformer
self.get_root_transformer().transform(out_value, context)
# end object if needed
if started_object:
self.end_object(out_value, context)
def transform(
self,
object_to_transform: AnyPDFType,
context: Optional[WriteTransformerContext] = None,
):
"""
This method writes an Image to a byte stream
"""
assert context is not None
assert context.destination is not None
assert isinstance(object_to_transform, PILImage.Image)
# get image bytes
contents = None
filter_name: Optional[Name] = None
try:
with io.BytesIO() as output:
assert isinstance(object_to_transform, PILImage.Image)
object_to_transform.save(output, format="JPEG")
contents = output.getvalue()
filter_name = Name("DCTDecode")
except Exception as e:
pass
if contents is None:
try:
# TODO : properly store PNG (instead of converting it)
with io.BytesIO() as output:
object_to_transform = self._convert_png_to_jpg(
object_to_transform)
assert isinstance(object_to_transform, PILImage.Image)
object_to_transform.save(output, format="JPEG")
contents = output.getvalue()
filter_name = Name("DCTDecode")
except Exception as e:
pass
assert contents is not None
# build corresponding Stream (XObject)
out_value = Stream()
out_value[Name("Type")] = Name("XObject")
out_value[Name("Subtype")] = Name("Image")
out_value[Name("Width")] = pDecimal(object_to_transform.width)
out_value[Name("Height")] = pDecimal(object_to_transform.height)
out_value[Name("Length")] = pDecimal(len(contents))
out_value[Name("Filter")] = filter_name
out_value[Name("BitsPerComponent")] = pDecimal(8)
out_value[Name("ColorSpace")] = Name("DeviceRGB")
out_value[Name("Bytes")] = contents
# copy reference
out_value.set_reference(
object_to_transform.get_reference()) # type: ignore [attr-defined]
# start object if needed
started_object = False
ref = out_value.get_reference() # type: ignore [attr-defined]
if ref is not None:
assert isinstance(ref, Reference)
if ref.object_number is not None and ref.byte_offset is None:
started_object = True
self._start_object(out_value, context)
# write stream
cl = context.compression_level
context.compression_level = 9
self.get_root_transformer().transform(out_value, context)
context.compression_level = cl
# end object if needed
if started_object:
self._end_object(out_value, context)
def transform(
self,
object_to_transform: AnyPDFType,
context: Optional[WriteTransformerContext] = None,
):
"""
This method writes a Stream to a byte stream
"""
assert context is not None
assert context.destination is not None
assert isinstance(object_to_transform, Stream)
# avoid resolving objects twice
object_ref: typing.Optional[
Reference] = object_to_transform.get_reference(
) # type: ignore [attr-defined]
if object_ref is not None and object_ref in context.resolved_references:
assert object_ref is not None
assert object_ref.object_number is not None
logger.debug(
"skip writing object %d %d R (already resolved)" %
(object_ref.object_number, object_ref.generation_number or 0))
return
# start object if needed
started_object = False
if object_ref is not None:
assert object_ref.object_number is not None
if object_ref.object_number is not None and object_ref.byte_offset is None:
started_object = True
self.start_object(object_to_transform, context)
context.resolved_references.append(object_ref)
# build stream dictionary
stream_dictionary = Dictionary()
# objects to turn into reference
queue: typing.List[AnyPDFType] = []
for k, v in object_to_transform.items():
if k in ["Bytes", "DecodedBytes"]:
continue
if (isinstance(v, Dictionary) or isinstance(v, List)
or isinstance(v, Stream)
) and v.can_be_referenced(): # type: ignore [union-attr]
stream_dictionary[k] = self.get_reference(v, context)
queue.append(v)
else:
stream_dictionary[k] = v
# if self.compression_level == 0, remove \Filter
if context.compression_level == 0 and Name(
"Filter") in stream_dictionary:
stream_dictionary.pop(Name("Filter"))
# handle compression
if "DecodedBytes" in object_to_transform:
if context.compression_level == 0:
bts = object_to_transform["DecodedBytes"]
else:
bts = zlib.compress(object_to_transform["DecodedBytes"],
context.compression_level)
stream_dictionary[Name("Length")] = pDecimal(len(bts))
else:
assert "Bytes" in object_to_transform
bts = object_to_transform["Bytes"]
# write stream dictionary
self.get_root_transformer().transform(stream_dictionary, context)
# write "stream"
context.destination.write(bytes("stream\n", "latin1"))
# write bytes
context.destination.write(bts)
# write "endstream"
context.destination.write(bytes("\nendstream\n", "latin1"))
# end object if needed
if started_object:
self.end_object(object_to_transform, context)
for e in queue:
self.get_root_transformer().transform(e, context)
def transform(
self,
object_to_transform: AnyPDFType,
context: Optional[WriteTransformerContext] = None,
):
"""
This method writes a List to a byte stream
"""
assert isinstance(object_to_transform, List)
assert context is not None
assert context.destination is not None
assert context.destination
# avoid resolving objects twice
object_ref: typing.Optional[
Reference] = object_to_transform.get_reference(
) # type: ignore [attr-defined]
if object_ref is not None and object_ref in context.resolved_references:
assert object_ref is not None
assert object_ref.object_number is not None
logger.debug(
"skip writing object %d %d R (already resolved)" %
(object_ref.object_number, object_ref.generation_number or 0))
return
# output value
out_value = List()
# objects to turn into reference
queue: typing.List[AnyPDFType] = []
for v in object_to_transform:
if (isinstance(v, Dictionary) or isinstance(v, List)
or isinstance(v, Stream) or isinstance(v, Image)
) and v.can_be_referenced(): # type: ignore [union-attr]
out_value.append(self.get_reference(v, context))
queue.append(v)
else:
out_value.append(v)
# start object if needed
started_object = False
if object_ref is not None:
assert object_ref.object_number is not None
if object_ref.object_number is not None and object_ref.byte_offset is None:
started_object = True
self.start_object(object_to_transform, context)
context.resolved_references.append(object_ref)
# write dictionary at current location
context.destination.write(bytes("[", "latin1"))
N = len(out_value)
for i, v in enumerate(out_value):
self.get_root_transformer().transform(v, context)
if i != N - 1:
context.destination.write(bytes(" ", "latin1"))
context.destination.write(bytes("]\n", "latin1"))
# end object if needed
if started_object:
self.end_object(object_to_transform, context)
for e in queue:
self.get_root_transformer().transform(e, context)
# return
return out_value