pdfbox/src/main/java/org/apache/pdfbox/text/PDFMarkedContentExtractor.java

/*
 * 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.text;

import java.io.IOException;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Deque;

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.PDXObject;
import org.apache.pdfbox.contentstream.operator.markedcontent.BeginMarkedContentSequence;
import org.apache.pdfbox.contentstream.operator.markedcontent.BeginMarkedContentSequenceWithProperties;
import org.apache.pdfbox.contentstream.operator.markedcontent.DrawObject;
import org.apache.pdfbox.contentstream.operator.markedcontent.EndMarkedContentSequence;

/**
 * This is an stream engine to extract the marked content of a pdf.
 *
 * @author Johannes Koch
 */
public class PDFMarkedContentExtractor extends LegacyPDFStreamEngine
{
    private boolean suppressDuplicateOverlappingText = true;
    private final List<PDMarkedContent> markedContents = new ArrayList<>();
    private final Deque<PDMarkedContent> currentMarkedContents = new ArrayDeque<>();
    private final Map<String, List<TextPosition>> characterListMapping = new HashMap<>();

    /**
     * Instantiate a new PDFTextStripper object.
     */
    public PDFMarkedContentExtractor() throws IOException
    {
        this(null);
    }

    /**
     * Constructor. Will apply encoding-specific conversions to the output text.
     *
     * @param encoding The encoding that the output will be written in.
     */
    public PDFMarkedContentExtractor(String encoding) throws IOException
    {
        addOperator(new BeginMarkedContentSequenceWithProperties());
        addOperator(new BeginMarkedContentSequence());
        addOperator(new EndMarkedContentSequence());
        addOperator(new DrawObject());
        // todo: DP - Marked Content Point
        // todo: MP - Marked Content Point with Properties
    }

    /**
     * @return the suppressDuplicateOverlappingText setting.
     */
    public boolean isSuppressDuplicateOverlappingText()
    {
        return suppressDuplicateOverlappingText;
    }

    /**
     * By default the class will attempt to remove text that overlaps each other. Word paints the
     * same character several times in order to make it look bold. By setting this to false all text
     * will be extracted, which means that certain sections will be duplicated, but better
     * performance will be noticed.
     *
     * @param suppressDuplicateOverlappingText The suppressDuplicateOverlappingText setting to set.
     */
    public void setSuppressDuplicateOverlappingText(boolean suppressDuplicateOverlappingText)
    {
        this.suppressDuplicateOverlappingText = suppressDuplicateOverlappingText;
    }

    /**
     * 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;
    }

    @Override
    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);
    }

    @Override
    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.
     */
    @Override
    protected void processTextPosition( TextPosition text )
    {
        boolean showCharacter = true;
        if( this.suppressDuplicateOverlappingText )
        {
            showCharacter = false;
            String textCharacter = text.getUnicode();
            float textX = text.getX();
            float textY = text.getY();
            List<TextPosition> sameTextCharacters =
                    this.characterListMapping.computeIfAbsent(textCharacter, k -> new ArrayList<>());

            // 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 (TextPosition sameTextCharacter : sameTextCharacters)
            {
                TextPosition character = sameTextCharacter;
                String charCharacter = character.getUnicode();
                float charX = character.getX();
                float charY = character.getY();
                //only want to suppress
                if( charCharacter != null &&
                        //charCharacter.equals( textCharacter ) &&
                        within( charX, textX, tolerance ) &&
                        within( charY,
                                textY,
                                tolerance ) )
                {
                    suppressCharacter = true;
                    break;
                }
            }
            if( !suppressCharacter )
            {
                sameTextCharacters.add( text );
                showCharacter = true;
            }
        }

        if( showCharacter )
        {
            List<TextPosition> 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 overlaid.  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 = textList.get(textList.size()-1);
                if(text.isDiacritic() && previousTextPosition.contains(text))
                {
                    previousTextPosition.mergeDiacritic(text);
                }
                /* 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);
                    textList.remove(textList.size()-1);
                    textList.add(text);
                }
                else
                {
                    textList.add(text);
                }
            }
            if (!this.currentMarkedContents.isEmpty())
            {
                this.currentMarkedContents.peek().addText(text);
            }
        }
    }

    public List<PDMarkedContent> getMarkedContents()
    {
        return this.markedContents;
    }
}