PTElementReader

@interface PTElementReader : NSObject

ElementReader can be used to parse and process content streams. ElementReader provides a convenient interface used to traverse the Element display list of a page. The display list representing graphical elements (such as text-runs, paths, images, shadings, forms, etc) is accessed using the intrinsic iterator. ElementReader automatically concatenates page contents spanning multiple streams and provides a mechanism to parse contents of sub-display lists (e.g. forms XObjects and Type3 fonts).

A sample use case for ElementReader is given below:

 ...
 ElementReader reader;
 reader.Begin(page);
 for (Element element=reader.Next(); element; element = reader.Next()) // Read page contents
 {
   switch (element.GetType())   {
     case Element::e_path: { // Process path data...
         const double* data = element.GetPathPoints();
         int sz = element.GetPointCount();
     }
     break;
     case Element::e_text:
         // ...
     break;
   }
 }
 reader.End();

For a full sample, please refer to ElementReader and ElementReaderAdvTest sample projects.

  • Undocumented

    Declaration

    Objective-C

    - (void)ReaderBeginWithPage: (PTPage*)page ocg_context:  (PTContext*)ocg_context;

    Swift

    func readerBegin(with page: PTPage!, ocg_context: PTContext!)
  • Begin processing a page.

    Note

    When page processing is completed, make sure to call ElementReader.End().

    Declaration

    Objective-C

    - (void)Begin:(PTPage *)page;

    Swift

    func begin(_ page: PTPage!)

    Parameters

    page

    A page to start processing.

    ocg_context

    An optional parameter used to specify the Optional Content (OC) Context that should be used when processing the page. When the OCG::Context is specified, Element::IsOCVisible() will return ‘true’ or ‘false’ depending on the visibility of the current Optional Content Group (OCG) and the states of flags in the given context.

  • Undocumented

    Declaration

    Objective-C

    - (void)ReaderBeginWithSDFObj: (PTObj*)content_stream resource_dict:  (PTObj*)resource_dict ocg_context:  (PTContext*)ocg_context;

    Swift

    func readerBegin(withSDFObj content_stream: PTObj!, resource_dict: PTObj!, ocg_context: PTContext!)
  • Note

    Every call to ElementReader::Next() destroys the current Element. Therefore, an Element becomes invalid after subsequent ElementReader::Next() operation.

    Declaration

    Objective-C

    - (PTElement *)Next;

    Swift

    func next() -> PTElement!

    Return Value

    a page Element or a ‘NULL’ element if the end of current-display list was reached. You may use GetType() to determine the type of the returned Element.

  • Note

    Every call to ElementReader::Next() destroys the current Element. Therefore, an Element becomes invalid after subsequent ElementReader::Next() operation.

    Declaration

    Objective-C

    - (PTElement *)Current;

    Swift

    func current() -> PTElement!

    Return Value

    the current Element or a ‘NULL’ Element. The current element is the one returned in the last call to Next().

  • When the current element is a form XObject you have the option to skip form processing (by not calling FormBegin()) or to open the form stream and continue Element traversal into the form.

    To open a form XObject display list use FormBegin() method. The Next() returned Element will be the first Element in the form XObject display list. Subsequent calls to Next() will traverse form’s display list until NULL is returned. At any point you can close the form sub-list using ElementReader::End() method. After the form display list is closed (using End()) the processing will return to the parent display list at the point where it left off before entering the form XObject.

    Declaration

    Objective-C

    - (void)FormBegin;

    Swift

    func formBegin()
  • A method used to spawn the sub-display list representing the tiling pattern of the current element in the ElementReader. You can call this method at any point as long as the current element is valid.

    To open a tiling pattern sub-display list use PatternBegin(pattern) method. The Next() returned Element will be the first Element in the pattern display list. Subsequent calls to Next() will traverse pattern’s display list until NULL is encountered. At any point you can close the pattern sub-list using ElementReader::End() method. After the pattern display list is closed, the processing will return to the parent display list at the point where pattern display list was spawned.

    Declaration

    Objective-C

    - (void)PatternBegin:(BOOL)fill_pattern reset_ctm_tfm:(BOOL)reset_ctm_tfm;

    Swift

    func patternBegin(_ fill_pattern: Bool, reset_ctm_tfm: Bool)

    Parameters

    fill_pattern

    If true, the filling pattern of the current element will be spawned; otherwise, the stroking pattern of the current element will be spawned. Note that the graphics state will be inherited from the parent content stream (the content stream in which the pattern is defined as a resource) automatically.

    reset_ctm_tfm

    An optional parameter used to indicate whether the pattern’s display list should set its initial CTM and transformation matrices to identity matrix. In general, we should leave it to be false.

  • A method used to spawn a sub-display list representing a Type3 Font glyph. You can call this method at any point as long as the current element in the ElementReader is a text element whose font type is type 3.

    To open a Type3 font sub-display list use Type3FontBegin() method. The Next() returned Element will be the first Element in the glyph’s display list. Subsequent calls to Next() will traverse glyph’s display list until NULL is returned. At any point you can close the glyph sub-list using ElementReader::End() method. After the glyph display list is closed, the processing will return to the parent display list at the point where glyph display list was spawned.

    Declaration

    Objective-C

    - (void)Type3FontBegin:(TRN_chardata *)char_data
             resource_dict:(PTObj *)resource_dict;

    Swift

    func type3FontBegin(_ char_data: TRN_chardata!, resource_dict: PTObj!)

    Parameters

    char_data

    The information about the glyph to process. You can get this information by dereferencing a CharIterator.

    resource_dict

    - An optional ‘/Resource’ dictionary parameter. If any glyph descriptions refer to named resources but Font Resource dictionary is absent, the names are looked up in the supplied resource dictionary.

  • Close the current display list.

    If the current display list is a sub-list created using FormBegin(), PatternBegin(), or Type3FontBegin() methods, the function will end the sub-list and will return processing to the parent display list at the point where it left off before entering the sub-list.

    Declaration

    Objective-C

    - (BOOL)End;

    Swift

    func end() -> Bool

    Return Value

    true if the closed display list is a sub-list or false if it is a root display list.

  • Declaration

    Objective-C

    - (PTGSChangesIterator *)GetChangesIterator;

    Swift

    func getChangesIterator() -> PTGSChangesIterator!

    Return Value

    an iterator to the beginning of the list containing identifiers of modified graphics state attributes since the last call to ClearChangeList(). The list can be consulted to determine which graphics states were modified between two Elements. Attributes are ordered in the same way as they are set in the content stream. Duplicate attributes are eliminated.

  • Declaration

    Objective-C

    - (BOOL)IsChanged:(PTGStateAttribute)attrib;

    Swift

    func isChanged(_ attrib: PTGStateAttribute) -> Bool

    Parameters

    attrib

    the GState attribute to test if it has been changed ClearChangeList().

    Return Value

    true if given GState attribute was changed since the last call to

  • Clear the list containing identifiers of modified graphics state attributes. The list of modified attributes is then accumulated during a subsequent call(s) to ElementReader.Next().

    Declaration

    Objective-C

    - (void)ClearChangeList;

    Swift

    func clearChangeList()
  • Declaration

    Objective-C

    - (void)AppendResource:(PTObj *)res;

    Swift

    func appendResource(_ res: PTObj!)

    Parameters

    res

    resource dictionary for finding images, fonts, etc.

  • Declaration

    Objective-C

    - (PTObj *)GetFont:(NSString *)name;

    Swift

    func getFont(_ name: String!) -> PTObj!

    Parameters

    name

    string of the name of the SDF/Cos object to get

    Return Value

    SDF/Cos object matching the specified name in the current resource dictionary. For ‘Page’ the name is looked up in the page’s /Resources/ dictionary. For Form XObjects, Patterns, and Type3 fonts that have a content stream within page content stream the specified resource is first looked-up in the resource dictionary of the inner stream. If the resource is not found, the name is looked up in the outer content stream’s resource dictionary. The function returns NULL if the resource was not found.

  • Note

    see ElementReader::GetFont

    Declaration

    Objective-C

    - (PTObj *)GetXObject:(NSString *)name;

    Swift

    func getXObject(_ name: String!) -> PTObj!

    Parameters

    name

    string of the name of the SDF/Cos object to get

  • Note

    see ElementReader::GetFont

    Declaration

    Objective-C

    - (PTObj *)GetShading:(NSString *)name;

    Swift

    func getShading(_ name: String!) -> PTObj!

    Parameters

    name

    string of the name of the SDF/Cos object to get

  • Note

    see ElementReader::GetFont

    Declaration

    Objective-C

    - (PTObj *)GetColorSpace:(NSString *)name;

    Swift

    func getColorSpace(_ name: String!) -> PTObj!

    Parameters

    name

    string of the name of the SDF/Cos object to get

  • Note

    see ElementReader::GetFont

    Declaration

    Objective-C

    - (PTObj *)GetPattern:(NSString *)name;

    Swift

    func getPattern(_ name: String!) -> PTObj!

    Parameters

    name

    string of the name of the SDF/Cos object to get

  • Note

    see ElementReader::GetFont

    Declaration

    Objective-C

    - (PTObj *)GetExtGState:(NSString *)name;

    Swift

    func getExtGState(_ name: String!) -> PTObj!

    Parameters

    name

    string of the name of the SDF/Cos object to get

  • Undocumented

    Declaration

    Objective-C

    - (instancetype)init;

    Swift

    init!()