PDFTron WebViewer

Class: TextExtractor

Core.PDFNet. TextExtractor

new TextExtractor()

TextExtractor is used to analyze a PDF page and extract words and logical structure within a given region. The resulting list of lines and words can be traversed element by element or accessed as a string buffer. The class also includes utility methods to extract PDF text as HTML or XML. Possible use case scenarios for TextExtractor include: - Converting PDF pages to text or XML for content repurposing. - Searching PDF pages for specific words or keywords. - Indexing large PDF repositories for indexing or content retrieval purposes (i.e. implementing a PDF search engine). - Classifying or summarizing PDF documents based on their text content. - Finding specific words for content editing purposes (such as splitting pages based on keywords etc). The main task of TextExtractor is to interpret PDF pages and offer a simple to use API to: - Normalize all text content to Unicode. - Extract inferred logical structure (word by word, line by line, or paragraph by paragraph). - Extract positioning information for every line, word, or a glyph. - Extract style information (such as information about the font, font size, font styles, etc) for every line, word, or a glyph. - Control the content analysis process. A number of options (such as removal of text obscured by images) is available to let the user direct the flow of content recognition algorithms that will meet their requirements. - Offer utility methods to convert PDF page content to text, XML, or HTML. Note: TextExtractor is analyzing only textual content of the page. This means that the rasterized (e.g. in scanned pages) or vectorized text (where glyphs are converted to path outlines) will not be recognized as text. Please note that it is still possible to extract this content using pdftron.PDF.ElementReader interface. In some cases TextExtractor may extract text that does not appear to be on the visible page (e.g. when text is obscured by an image or a rectangle). In these situations it is possible to use processing flags such as 'e_remove_hidden_text' and 'e_no_invisible_text' to remove hidden text. A sample use case (in C++): 
... Initialize PDFNet ...
PDFDoc doc(filein);
doc.InitSecurityHandler();
Page page = *doc.PageBegin();
TextExtractor txt;
txt.Begin(page, 0, TextExtractor::e_remove_hidden_text);
UString text;
txt.GetAsText(text);
// or traverse words one by one...
TextExtractor::Line line = txt.GetFirstLine(), lend;
TextExtractor::Word word, wend;
for (; line!=lend; line=line.GetNextLine()) {
 for (word=line.GetFirstWord(); word!=wend; word=word.GetNextWord()) {
   text.Assign(word.GetString(), word.GetStringLen());
   cout << text << '\n';
 }
}
A sample use case (in C#): 
... Initialize PDFNet ...
PDFDoc doc = new PDFDoc(filein);
doc.InitSecurityHandler();
Page page = doc.PageBegin().Current();
TextExtractor txt = new TextExtractor();
txt.Begin(page, 0, TextExtractor.ProcessingFlags.e_remove_hidden_text);
string text = txt.GetAsText();
// or traverse words one by one...
TextExtractor.Word word;
for (TextExtractor.Line line = txt.GetFirstLine(); line.IsValid(); line=line.GetNextLine()) {
  for (word=line.GetFirstWord(); word.IsValid(); word=word.GetNextWord()) {
    Console.WriteLine(word.GetString());
  }
}
For full sample code, please take a look at TextExtract sample project.

Extends

Members

<static> ProcessingFlags

Type:
  • number
Properties:
Name Type Description
e_no_ligature_exp number
e_no_dup_remove number
e_punct_break number
e_remove_hidden_text number
e_no_invisible_text number
e_no_watermarks number
e_extract_using_zorder number

<static> XMLOutputFlags

Type:
  • number
Properties:
Name Type Description
e_words_as_elements number
e_output_bbox number
e_output_style_info number

Methods

<static> create()

Constructor and destructor
Returns:
A promise that resolves to an object of type: "PDFNet.TextExtractor"
Type
Promise.<Core.PDFNet.TextExtractor>

begin(page [, clip_ptr] [, flags])

Start reading the page.
Parameters:
Name Type Argument Description
page Core.PDFNet.Page Page to read.
clip_ptr Core.PDFNet.Rect <optional>
 An optional clipping rectangle. This parameter can be used to selectively read text from a given rectangle.
flags number <optional>
 A list of ProcessingFlags used to control text extraction algorithm.
Returns:
Type
Promise.<void>

destroy()

Destructor
Inherited From:
Returns:
Type
Promise.<void>

getAsText( [dehyphen])

get all words in the current selection as a single string.
Parameters:
Name Type Argument Description
dehyphen boolean <optional>
 If true, finds and removes hyphens that split words across two lines. Hyphens are often used a the end of lines as an indicator that a word spans two lines. Hyphen detection enables removal of hyphen character and merging of text runs to form a single word. This option has no effect on Tagged PDF files.
Returns:
A promise that resolves to an object of type: "string"
Type
Promise.<string>

getAsXML( [xml_output_flags])

get text content in a form of an XML string.
Parameters:
Name Type Argument Description
xml_output_flags number <optional>
 flags controlling XML output. For more information, please see TextExtract::XMLOutputFlags. XML output will be encoded in UTF-8 and will have the following structure: 

 
  
   
     PDFNet
     SDK
     is
     ...
The above XML output was generated by passing the following union of flags in the call to GetAsXML(): (TextExtractor::e_words_as_elements | TextExtractor::e_output_bbox | TextExtractor::e_output_style_info) In case 'xml_output_flags' was not specified, the default XML output would look as follows: PDFNet SDK is an amazingly comprehensive, high-quality PDF developer toolkit... levels. Using the PDFNet PDF library, ... ...
Returns:
A promise that resolves to an object of type: "string"
Type
Promise.<string>

getFirstLine()

Returns:
A promise that resolves to the first line of text on the selected page. Note: To traverse the list of all text lines on the page use line.GetNextLine(). Note: To traverse the list of all word on a given line use line.GetFirstWord().
Type
Promise.<Core.PDFNet.TextExtractorLine>

getHighlights(char_ranges)

Get a Highlights object based on an array of character ranges.
Parameters:
Name Type Description
char_ranges Array.<object> an array of character ranges to be highlighted, such as [{ "index": 1, "length": 10 }, { "index": 100, "length": 20 }]
Returns:
A promise that resolves to an object of type: "Highlights", containing the selected characters.
Type
Promise.<Core.PDFNet.Highlights>

getNumLines()

Returns:
A promise that resolves to the number of lines of text on the selected page.
Type
Promise.<number>

getQuads(mtx, quads, quads_size)

[CURRENTLY BUGGED]
Parameters:
Name Type Description
mtx Core.PDFNet.Matrix2D The quadrilateral representing a tight bounding box
quads number n
quads_size number n for this word (in unrotated page coordinates).
Returns:
Type
Promise.<void>

getRightToLeftLanguage()

Returns:
A promise that resolves to the directionality of text extractor.
Type
Promise.<boolean>

getTextUnderAnnot(annot)

Get all the characters that intersect an annotation.
Parameters:
Name Type Description
annot Core.PDFNet.Annot The annotation to intersect with.
Returns:
A promise that resolves to an object of type: "string"
Type
Promise.<string>

getWordCount()

Returns:
A promise that resolves to the number of words on the page.
Type
Promise.<number>

setOCGContext(ctx)

Sets the Optional Content Group (OCG) context that should be used when processing the document. This function can be used to change the current OCG context. Optional content (such as PDF layers) will be selectively processed based on the states of optional content groups in the given context.
Parameters:
Name Type Description
ctx Core.PDFNet.OCGContext Optional Content Group (OCG) context, or NULL if TextExtractor should process all content on the page.
Returns:
Type
Promise.<void>

setRightToLeftLanguage(rtl)

Sets the directionality of text extractor. Must be called before the processing of a page started.
Parameters:
Name Type Description
rtl boolean mode reverses the directionality of TextExtractor algorithm.
Returns:
Type
Promise.<void>

takeOwnership()

Take the ownership of this object, so that PDFNet.runWithCleanup won't destroy this object.
Inherited From:
Returns:
Type
void