com.itextpdf.text.pdf.parser.SimpleTextExtractionStrategy Maven / Gradle / Ivy
/*
*
* This file is part of the iText (R) project.
Copyright (c) 1998-2017 iText Group NV
* Authors: Kevin Day, Bruno Lowagie, Paulo Soares, et al.
*
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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
}
}