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The Apache PDFBox library is an open source Java tool for working with PDF documents.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.pdfbox.util;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Stack;
import org.apache.pdfbox.cos.COSDictionary;
import org.apache.pdfbox.cos.COSName;
import org.apache.pdfbox.pdmodel.documentinterchange.markedcontent.PDMarkedContent;
import org.apache.pdfbox.pdmodel.graphics.xobject.PDXObject;
/**
* This is an stream engine to extract the marked content of a pdf.
* @author koch
* @version $Revision$
*/
public class PDFMarkedContentExtractor extends PDFStreamEngine
{
private boolean suppressDuplicateOverlappingText = true;
private List markedContents = new ArrayList();
private Stack currentMarkedContents = new Stack();
private Map> characterListMapping =
new HashMap>();
/**
* encoding that text will be written in (or null).
*/
protected String outputEncoding;
/**
* The normalizer is used to remove text ligatures/presentation forms
* and to correct the direction of right to left text, such as Arabic and Hebrew.
*/
private TextNormalize normalize = null;
/**
* Instantiate a new PDFTextStripper object. This object will load
* properties from PDFMarkedContentExtractor.properties and will not
* do anything special to convert the text to a more encoding-specific
* output.
*
* @throws IOException If there is an error loading the properties.
*/
public PDFMarkedContentExtractor() throws IOException
{
super( ResourceLoader.loadProperties(
"org/apache/pdfbox/resources/PDFMarkedContentExtractor.properties", true ) );
this.outputEncoding = null;
this.normalize = new TextNormalize(this.outputEncoding);
}
/**
* Instantiate a new PDFTextStripper object. Loading all of the operator mappings
* from the properties object that is passed in. Does not convert the text
* to more encoding-specific output.
*
* @param props The properties containing the mapping of operators to PDFOperator
* classes.
*
* @throws IOException If there is an error reading the properties.
*/
public PDFMarkedContentExtractor( Properties props ) throws IOException
{
super( props );
this.outputEncoding = null;
this.normalize = new TextNormalize(this.outputEncoding);
}
/**
* Instantiate a new PDFTextStripper object. This object will load
* properties from PDFMarkedContentExtractor.properties and will apply
* encoding-specific conversions to the output text.
*
* @param encoding The encoding that the output will be written in.
* @throws IOException If there is an error reading the properties.
*/
public PDFMarkedContentExtractor( String encoding ) throws IOException
{
super( ResourceLoader.loadProperties(
"org/apache/pdfbox/resources/PDFMarkedContentExtractor.properties", true ));
this.outputEncoding = encoding;
this.normalize = new TextNormalize(this.outputEncoding);
}
/**
* This will determine of two floating point numbers are within a specified variance.
*
* @param first The first number to compare to.
* @param second The second number to compare to.
* @param variance The allowed variance.
*/
private boolean within( float first, float second, float variance )
{
return second > first - variance && second < first + variance;
}
public void beginMarkedContentSequence(COSName tag, COSDictionary properties)
{
PDMarkedContent markedContent = PDMarkedContent.create(tag, properties);
if (this.currentMarkedContents.isEmpty())
{
this.markedContents.add(markedContent);
}
else
{
PDMarkedContent currentMarkedContent =
this.currentMarkedContents.peek();
if (currentMarkedContent != null)
{
currentMarkedContent.addMarkedContent(markedContent);
}
}
this.currentMarkedContents.push(markedContent);
}
public void endMarkedContentSequence()
{
if (!this.currentMarkedContents.isEmpty())
{
this.currentMarkedContents.pop();
}
}
public void xobject(PDXObject xobject)
{
if (!this.currentMarkedContents.isEmpty())
{
this.currentMarkedContents.peek().addXObject(xobject);
}
}
/**
* This will process a TextPosition object and add the
* text to the list of characters on a page. It takes care of
* overlapping text.
*
* @param text The text to process.
*/
protected void processTextPosition( TextPosition text )
{
boolean showCharacter = true;
if( this.suppressDuplicateOverlappingText )
{
showCharacter = false;
String textCharacter = text.getCharacter();
float textX = text.getX();
float textY = text.getY();
List sameTextCharacters = this.characterListMapping.get( textCharacter );
if( sameTextCharacters == null )
{
sameTextCharacters = new ArrayList();
this.characterListMapping.put( textCharacter, sameTextCharacters );
}
// RDD - Here we compute the value that represents the end of the rendered
// text. This value is used to determine whether subsequent text rendered
// on the same line overwrites the current text.
//
// We subtract any positive padding to handle cases where extreme amounts
// of padding are applied, then backed off (not sure why this is done, but there
// are cases where the padding is on the order of 10x the character width, and
// the TJ just backs up to compensate after each character). Also, we subtract
// an amount to allow for kerning (a percentage of the width of the last
// character).
//
boolean suppressCharacter = false;
float tolerance = (text.getWidth()/textCharacter.length())/3.0f;
for( int i=0; i textList = new ArrayList();
/* In the wild, some PDF encoded documents put diacritics (accents on
* top of characters) into a separate Tj element. When displaying them
* graphically, the two chunks get overlayed. With text output though,
* we need to do the overlay. This code recombines the diacritic with
* its associated character if the two are consecutive.
*/
if(textList.isEmpty())
{
textList.add(text);
}
else
{
/* test if we overlap the previous entry.
* Note that we are making an assumption that we need to only look back
* one TextPosition to find what we are overlapping.
* This may not always be true. */
TextPosition previousTextPosition = (TextPosition)textList.get(textList.size()-1);
if(text.isDiacritic() && previousTextPosition.contains(text))
{
previousTextPosition.mergeDiacritic(text, this.normalize);
}
/* If the previous TextPosition was the diacritic, merge it into this
* one and remove it from the list. */
else if(previousTextPosition.isDiacritic() && text.contains(previousTextPosition))
{
text.mergeDiacritic(previousTextPosition, this.normalize);
textList.remove(textList.size()-1);
textList.add(text);
}
else
{
textList.add(text);
}
}
if (!this.currentMarkedContents.isEmpty())
{
this.currentMarkedContents.peek().addText(text);
}
}
}
public List getMarkedContents()
{
return this.markedContents;
}
}