itextpdf-master/itext/src/main/java/com/itextpdf/text/pdf/parser/SimpleTextExtractionStrategy.java
/*
 *
 * This file is part of the iText (R) project.
    Copyright (c) 1998-2022 iText Group NV
 * Authors: Kevin Day, Bruno Lowagie, Paulo Soares, et al.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License version 3
 * as published by the Free Software Foundation with the addition of the
 * following permission added to Section 15 as permitted in Section 7(a):
 * FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
 * ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
 * OF THIRD PARTY RIGHTS
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Affero General Public License for more details.
 * You should have received a copy of the GNU Affero General Public License
 * along with this program; if not, see http://www.gnu.org/licenses or write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA, 02110-1301 USA, or download the license from the following URL:
 * http://itextpdf.com/terms-of-use/
 *
 * The interactive user interfaces in modified source and object code versions
 * of this program must display Appropriate Legal Notices, as required under
 * Section 5 of the GNU Affero General Public License.
 *
 * In accordance with Section 7(b) of the GNU Affero General Public License,
 * a covered work must retain the producer line in every PDF that is created
 * or manipulated using iText.
 *
 * You can be released from the requirements of the license by purchasing
 * a commercial license. Buying such a license is mandatory as soon as you
 * develop commercial activities involving the iText software without
 * disclosing the source code of your own applications.
 * These activities include: offering paid services to customers as an ASP,
 * serving PDFs on the fly in a web application, shipping iText with a closed
 * source product.
 *
 * For more information, please contact iText Software Corp. at this
 * address: sales@itextpdf.com
 */
package com.itextpdf.text.pdf.parser;


/**
 * A simple text extraction renderer.
 * 
 * This renderer keeps track of the current Y position of each string.  If it detects
 * that the y position has changed, it inserts a line break into the output.  If the
 * PDF renders text in a non-top-to-bottom fashion, this will result in the text not
 * being a true representation of how it appears in the PDF.
 * 
 * This renderer also uses a simple strategy based on the font metrics to determine if
 * a blank space should be inserted into the output.
 * 
 * @since	2.1.5
 */
public class SimpleTextExtractionStrategy implements TextExtractionStrategy {

    private Vector lastStart;
    private Vector lastEnd;
    
    /** used to store the resulting String. */
    private final StringBuffer result = new StringBuffer();;

    /**
     * Creates a new text extraction renderer.
     */
    public SimpleTextExtractionStrategy() {
    }

    /**
     * @since 5.0.1
     */
    public void beginTextBlock() {
    }

    /**
     * @since 5.0.1
     */
    public void endTextBlock() {
    }
    
    /**
     * Returns the result so far.
     * @return	a String with the resulting text.
     */
    public String getResultantText(){
        return result.toString();
    }

    /**
     * Used to actually append text to the text results.  Subclasses can use this to insert
     * text that wouldn't normally be included in text parsing (e.g. result of OCR performed against
     * image content)
     * @param text the text to append to the text results accumulated so far
     */
    protected final void appendTextChunk(CharSequence text){
    	result.append(text);
    }
    
    /**
     * Captures text using a simplified algorithm for inserting hard returns and spaces
     * @param	renderInfo	render info
     */
    public void renderText(TextRenderInfo renderInfo) {
        boolean firstRender = result.length() == 0;
        boolean hardReturn = false;

        LineSegment segment = renderInfo.getBaseline();
        Vector start = segment.getStartPoint();
        Vector end = segment.getEndPoint();
        
        if (!firstRender){
            Vector x0 = start;
            Vector x1 = lastStart;
            Vector x2 = lastEnd;
            
            // see http://mathworld.wolfram.com/Point-LineDistance2-Dimensional.html
            float dist = (x2.subtract(x1)).cross((x1.subtract(x0))).lengthSquared() / x2.subtract(x1).lengthSquared();

            float sameLineThreshold = 1f; // we should probably base this on the current font metrics, but 1 pt seems to be sufficient for the time being
            if (dist > sameLineThreshold)
                hardReturn = true;
            
            // Note:  Technically, we should check both the start and end positions, in case the angle of the text changed without any displacement
            // but this sort of thing probably doesn't happen much in reality, so we'll leave it alone for now
        }
        
        if (hardReturn){
            //System.out.println("<< Hard Return >>");
        	appendTextChunk("\n");
        } else if (!firstRender){ 
            if (result.charAt(result.length()-1) != ' ' && renderInfo.getText().length() > 0 && renderInfo.getText().charAt(0) != ' '){ // we only insert a blank space if the trailing character of the previous string wasn't a space, and the leading character of the current string isn't a space
                float spacing = lastEnd.subtract(start).length();
                if (spacing > renderInfo.getSingleSpaceWidth()/2f){
                	appendTextChunk(" ");
                    //System.out.println("Inserting implied space before '" + renderInfo.getText() + "'");
                }
            }
        } else {
            //System.out.println("Displaying first string of content '" + text + "' :: x1 = " + x1);
        }
        
        //System.out.println("[" + renderInfo.getStartPoint() + "]->[" + renderInfo.getEndPoint() + "] " + renderInfo.getText());
        appendTextChunk(renderInfo.getText());

        lastStart = start;
        lastEnd = end;
        
    }

    /**
     * no-op method - this renderer isn't interested in image events
     * @see com.itextpdf.text.pdf.parser.RenderListener#renderImage(com.itextpdf.text.pdf.parser.ImageRenderInfo)
     * @since 5.0.1
     */
    public void renderImage(ImageRenderInfo renderInfo) {
        // do nothing - we aren't tracking images in this renderer
    }


}
