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Classes and Modules

class HexaPDF::Document

Parent Object

HexaPDF::Document ↑

Represents a PDF document.

A PDF document essentially consists of (indirect) objects, so the main job of this class is to provide methods for working with these objects. However, since a PDF document may also be incrementally updated and can therefore contain one or more revisions, there are also methods for working with these revisions (see Revisions for details).

Additionally, there are many convenience methods for easily accessing the most important PDF functionality, like encrypting a document (encrypt), working with digital signatures (signatures), accessing the interactive form data (acro_form), working with the pages (pages), fonts (fonts) and images (images).

Note: This class provides the basis for working with a PDF document. The higher PDF functionality is not implemented here but either in the appropriate PDF type classes or in special convenience classes. All this functionality can be accessed via the convenience methods described above.

Available Message Hooks ↑

The document object provides a basic message dispatch system via register_listener and dispatch_message.

Following messages are used by HexaPDF itself:

:complete_objects

This message is called before the first step of writing a document. Listeners should complete PDF objects that are missing some information.

For example, the font system uses this message to complete the font objects with information that is only available once all the used glyphs are known.

:before_write

This message is called before a document is actually serialized and written.

Constants

UNSET

Attributes

config[R]

The configuration object for the document.

See Configuration for details.

revisions[R]

The revisions of the document.

See Revisions.

Public Class Methods

new(io: nil, decryption_opts: {}, config: {})

Creates a new PDF document, either an empty one or one read from the provided io.

When an IO object is provided and it contains an encrypted PDF file, it is automatically decrypted behind the scenes. The decryption_opts argument has to be set appropriately in this case. In case this is not wanted, the configuration option ‘document.auto_decrypt’ needs to be used.

Options:

io

If an IO object is provided, then this document can read PDF objects from this IO object, otherwise it can only contain created PDF objects.

decryption_opts

A hash with options for decrypting the PDF objects loaded from the IO. The PDF standard security handler expects a :password key to be set to either the user or owner password of the PDF file.

config

A hash with configuration options that is deep-merged into the default configuration (see HexaPDF::DefaultDocumentConfiguration, meaning that direct sub-hashes are merged instead of overwritten.

open(filename, **docargs) → doc
open(filename, **docargs) {|doc| block} → obj

Creates a new PDF Document object for the given file.

Depending on whether a block is provided, the functionality is different:

  • If no block is provided, the whole file is instantly read into memory and the PDF Document created for it is returned.

  • If a block is provided, the file is opened and a PDF Document is created for it. The created document is passed as an argument to the block and when the block returns the associated file object is closed. The value of the block will be returned.

The block version is useful, for example, when you are dealing with a large file and you only need a small portion of it.

The provided keyword arguments (except io) are passed on unchanged to Document.new.

Public Instance Methods

acro_form(create: false)

Returns the main AcroForm object for dealing with interactive forms.

The meaning of the create argument is detailed at Type::Catalog#acro_form.

See: Type::AcroForm::Form

add(obj, **wrap_opts) → indirect_object

Adds the object to the document and returns the wrapped indirect object.

The object can either be a native Ruby object (Hash, Array, Integer, …) or a HexaPDF::Object. If it is not the latter, wrap is called with the object and the additional keyword arguments.

See: wrap, Revisions#add_object

cache(pdf_data, key, value = UNSET, update: false) { |: value)| ... }

Caches and returns the given value or the value of the given block using the given pdf_data and key arguments as composite cache key.

If a cached value already exists and update is false, the cached value is just returned. If update is set to true, an update of the cached value is forced.

This facility can be used to cache expensive operations in PDF objects that are easy to compute again.

Use clear_cache to clear the cache if necessary.

cached?(pdf_data, key)

Returns true if there is a value cached for the composite key consisting of the given pdf_data and key objects.

See: cache

catalog()

Returns the document’s catalog, the root of the object tree.

See: Type::Catalog

clear_cache(pdf_data = nil)

Clears all cached data or, if a Object::PDFData object is given, just the cache for this one object.

It is not recommended to clear the whole cache! Better clear the cache for individual PDF objects!

See: cache, cached?

delete(ref)
delete(oid)

Deletes the indirect object specified by an exact reference or by an object number from the document.

See: Revisions#delete_object

deref(obj)

Dereferences the given object.

Returns the object itself if it is not a reference, or the indirect object specified by the reference.

destinations()

Returns the Destinations object that provides convenience methods for working with destination objects.

dispatch_message(name, *args)

Dispatches the message name with the given arguments to all registered listeners.

See the main Document documentation for an overview of messages that are used by HexaPDF itself.

See: register_listener

duplicate()

Returns an in-memory copy of the PDF document.

In the context of this method this means that the returned PDF document contains the same PDF object tree as this document, starting at the trailer. A possibly set encryption is not transferred to the returned document.

Note: If this PDF document was created from scratch or if it is an existing document that was modified, the following commands need to be run on this document beforehand:

doc.dispatch_message(:complete_objects)
doc.validate

This ensures that all the necessary PDF structures set-up correctly.

each(only_current: true, only_loaded: false) {|obj| block }
each(only_current: true, only_loaded: false) {|obj, rev| block }
each(only_current: true, only_loaded: false) → Enumerator

Yields every object and the revision it is in.

If only_current is true, only the current version of each object is yielded, otherwise all objects from all revisions. Note that it is normally not necessary or useful to retrieve all objects from all revisions and if it is still done that care has to be taken to avoid an invalid document state.

If only_loaded is true, only the already loaded objects are yielded.

For details see Revisions#each_object

encrypt(name: :Standard, **options)

Encrypts the document.

Encryption is done by setting up a security handler for this purpose and populating the trailer’s Encrypt dictionary accordingly. The actual encryption, however, is only done when writing the document.

The security handler used for encrypting is selected via the name argument. All other arguments are passed on to the security handler.

If the document should not be encrypted, the name argument has to be set to nil. This removes the security handler and deletes the trailer’s Encrypt dictionary.

See: Encryption::SecurityHandler#set_up_encryption and Encryption::StandardSecurityHandler::EncryptionOptions for possible encryption options.

Examples:

document.encrypt(name: nil)  # remove the existing encryption
document.encrypt(algorithm: :aes, key_length: 256, permissions: [:print, :extract_content]
encrypted?()

Returns true if the document is encrypted.

files()

Returns the Files object that provides convenience methods for working with embedded files.

fonts()

Returns the Fonts object that provides convenience methods for working with the fonts used in the PDF file.

images()

Returns the Images object that provides convenience methods for working with images (e.g. adding them to the PDF or listing them).

import(obj) → imported_object

Imports the given object from a different HexaPDF::Document instance and returns the imported object.

If the same argument is provided in multiple invocations, the import is done only once and the previously imported object is returned.

Note: If you first create a PDF document from scratch or if you modify an existing document, and then want to import objects from it into another PDF document, you need to run the following on the source document:

doc.dispatch_message(:complete_objects)
doc.validate

This ensures that the source document has all the necessary PDF structures set-up correctly.

See: Importer

layout()

Returns the Layout object that provides convenience methods for working with the HexaPDF::Layout classes for document layout.

metadata()

Returns the Metadata object that provides a convenience interface for working with the document metadata.

Note that invoking this method means that, depending on the settings, the info dictionary as well as the metadata stream will be overwritten when the document gets written. See the “Caveats” section in the Metadata documentation.

object(ref) → obj or nil
object(oid) → obj or nil

Returns the current version of the indirect object for the given exact reference (see Reference) or for the given object number.

For references to unknown objects, nil is returned but free objects are represented by a PDF Null object, not by nil!

See: Revisions#object

object?(ref) → true or false
object?(oid) → true or false

Returns true if the the document contains an indirect object for the given exact reference (see Reference) or for the given object number.

Even though this method might return true for some references, object may return nil because this method takes all revisions into account. Also see the discussion on each for more information.

See: Revisions#object?

optional_content()

Returns the main object for working with optional content (a.k.a. layers).

See: Type::Catalog#optional_content

outline()

Returns the entry object to the document outline (a.k.a. bookmarks).

See: Type::Outline

pages()

Returns the Pages object that provides convenience methods for working with the pages of the PDF file.

See: Pages, Type::PageTreeNode

register_listener(name, callable) → callable
register_listener(name) {|*args| block} → block

Registers the given listener for the message name.

If callable is provided, it needs to be an Object responding to call. Otherwise the block has to be provided. The arguments that are provided to the call method depend on the message.

See: dispatch_message

security_handler()

Returns the security handler that is used for decrypting or encrypting the document, or nil if none is set.

  • If the document was created by reading an existing file and the document was automatically decrypted, then this method returns the handler for decrypting.

  • Once the encrypt method is called, the specified security handler for encrypting is returned.

sign(file_or_io, handler: :default, signature: nil, write_options: {}, **handler_options)

Signs the document and writes it to the given file or IO object.

For details on the arguments file_or_io, signature and write_options see DigitalSignature::Signatures#add.

The signing handler to be used is determined by the handler argument together with the rest of the keyword arguments (see DigitalSignature::Signatures#signing_handler for details).

If not changed, the default signing handler is DigitalSignature::Signing::DefaultHandler.

Note: Once signing is done the document cannot be changed anymore since it was written during the signing process. If a document needs to be signed multiple times, it needs to be loaded again afterwards.

signatures()

Returns a DigitalSignature::Signatures object that allows working with the digital signatures of this document.

signed?()

Returns true if the document is signed, i.e. contains digital signatures.

task(name, **opts, &block)

Executes the given task and returns its result.

Tasks provide an extensible way for performing operations on a PDF document without cluttering the Document interface.

See: Task

trailer()

Returns the trailer dictionary for the document.

See: Type::Trailer

unwrap(obj) → unwrapped_obj

Recursively unwraps the object to get native Ruby objects (i.e. Hash, Array, Integer, … instead of HexaPDF::Reference and HexaPDF::Object).

validate(auto_correct: true, only_loaded: false) { |msg, correctable, object| ... }

Validates all current objects, or, if only_loaded is true, only loaded objects, with optional auto-correction, and returns true if everything is fine.

If a block is given, it is called on validation problems.

See Object#validate for more information.

version()

Returns the PDF document’s version as string (e.g. ‘1.4’).

This method takes the file header version and the catalog’s /Version key into account. If a version has been set manually and the catalog’s /Version key refers to a later version, the later version is used.

See: PDF2.0 s7.2.2

version=(value)

Sets the version of the PDF document.

The argument value must be a string in the format ‘M.N’ where M is the major version and N the minor version (e.g. ‘1.4’ or ‘2.0’).

wrap(obj, type: nil, subtype: nil, oid: nil, gen: nil, stream: nil)

Wraps the given object inside a HexaPDF::Object (sub)class which allows one to use convenience functions to work with the object.

The obj argument can also be a HexaPDF::Object object so that it can be re-wrapped if necessary.

The class of the returned object is always a subclass of HexaPDF::Object (or of HexaPDF::Stream if stream is given). Which subclass is used, depends on the values of the type and subtype options as well as on the ‘object.type_map’ and ‘object.subtype_map’ global configuration options:

  • First type is used to try to determine the class. If it is not provided and if obj is a hash with a :Type field, the value of this field is used instead. If the resulting object is already a Class object, it is used, otherwise the type is looked up in ‘object.type_map’.

  • If subtype is provided or can be determined because obj is a hash with a :Subtype or :S field, the type and subtype together are used to look up a special subtype class in ‘object.subtype_map’.

    Additionally, if there is no type but a subtype, all required fields of the subtype class need to have values; otherwise the subtype class is not used. This is done to better prevent invalid mappings when only partial knowledge (:Type key is missing) is available.

  • If there is no valid class after the above steps, HexaPDF::Stream is used if a stream is given, HexaPDF::Dictionary if the given object is a hash, HexaPDF::PDFArray if it is an array or else HexaPDF::Object.

Options:

:type

(Symbol or Class) The type of a PDF object that should be used for wrapping. This could be, for example, :Pages. If a class object is provided, it is used directly instead of determining the class through the type detection system.

:subtype

(Symbol) The subtype of a PDF object which further qualifies a type. For example, image objects in PDF have a type of :XObject and a subtype of :Image.

:oid

(Integer) The object number that should be set on the wrapped object. Defaults to 0 or the value of the given object’s object number.

:gen

(Integer) The generation number that should be set on the wrapped object. Defaults to 0 or the value of the given object’s generation number.

:stream

(String or StreamData) The stream object which should be set on the wrapped object.

write(filename, incremental: false, validate: true, update_fields: true, optimize: false) → [start_xref, section]
write(io, incremental: false, validate: true, update_fields: true, optimize: false) → [start_xref, section]

Writes the document to the given file (in case io is a String) or IO stream. Returns the file position of the start of the last cross-reference section and the last XRefSection object written.

Before the document is written, it is validated using validate and an error is raised if the document is not valid. However, this step can be skipped if needed.

Options:

incremental

Use the incremental writing mode which just adds a new revision to an existing document. This is needed, for example, when modifying a signed PDF and the original signature should stay valid.

See: PDF2.0 s7.5.6

validate

Validates the document and raises an error if an uncorrectable problem is found.

update_fields

Updates the /ID field in the trailer dictionary as well as the /ModDate field in the trailer’s /Info dictionary so that it is clear that the document has been updated.

optimize

Optimize the file size by using object and cross-reference streams. This will raise the PDF version to at least 1.5.

write_to_string(**args)

Writes the document to a string and returns the string.

See write for further information and details on the available arguments.