HexaPDFclass HexaPDF::
| Parent | HexaPDF::Stream |
|---|
Represents PDF type XRef, cross-reference streams.
A cross-reference stream is used as a more compact representation for an cross-reference section and trailer dictionary. The trailer dictionary is incorporated into the stream dictionary and the cross-reference section entries are stored in the stream itself, compressed to save space.
How are Cross-reference Streams Used?¶ ↑
Cross-reference stream objects are only used when parsing or writing a PDF document.
When a file is read and a cross-reference stream is found, it is loaded and its information is stored in a HexaPDF::Revision object. So from a user’s perspective nothing changes when a cross-reference stream instead of a cross-reference section and trailer is encountered.
This also means that all information stored in a cross-reference stream between parsing and writing is discarded when the PDF document gets written!
Upon writing a revision it is checked whether that revision contains a cross-reference stream object. If it does the cross-reference stream object is updated with the cross-reference section and trailer information and then written. Otherwise a normal cross-reference section plus trailer are written.
See: PDF2.0 s7.5.8
Field Definitions
| Name | Type/Allowed Values | Required | Default Value |
|---|---|---|---|
| Length | Integer | false | nil |
| Filter | Symbol or HexaPDF::PDFArray or Array | false | nil |
| DecodeParms | HexaPDF::Dictionary or HexaPDF::PDFArray or Hash or Array | false | nil |
| F | HexaPDF::Type::FileSpecification or Hash or String | false | nil |
| FFilter | Symbol or HexaPDF::PDFArray or Array | false | nil |
| FDecodeParms | HexaPDF::Dictionary or HexaPDF::PDFArray or Hash or Array | false | nil |
| DL | Integer | false | nil |
| Type | Symbol | true | :XRef |
| Size | Integer | true | nil |
| Index | HexaPDF::PDFArray or Array | false | nil |
| Prev | Integer | false | nil |
| W | HexaPDF::PDFArray or Array | true | nil |
Public Instance Methods
Returns a hash with the entries that represent the file trailer part of the cross-reference stream’s dictionary.
See: Type::Trailer
Makes this cross-reference stream represent the data in the given HexaPDF::XRefSection and Type::Trailer.
The xref_section needs to contain an entry for this cross-reference stream and it is necessary that this entry is the one with the highest byte position (for calculating the correct /W entry).
The given cross-reference section is not stored but only used to rewrite the associated stream to reflect the cross-reference section. The dictionary is updated with the information from the trailer and the needed entries for the cross-reference section.
If there are changes to the cross-reference section or trailer, this method has to be invoked again.
Returns an XRefSection that represents the content of this cross-reference stream.
Each invocation returns a new XRefSection object based on the current data in the associated stream and dictionary.