Feature request for filtering TextPosition in PDFTextStripperByArea and PDFTextStripper

[Hengyu Weng <ap...@gmail.com>]

Sometimes the watermark will overlap with normal text which we want to
extract, so it would be great if it is possible to insert a filter and skip
some useless TextPositons (e.g. the text of the watermark may have a
rotation). I think the 'writePage' method in 'PDFTextStripper' is an
appropriate place to add this filter, but I found it is difficult to
override this method as it refers to a lot of private members, and
PDFTextStripper extends LegacyPDFStreamEngine, which is a non-public class,
which makes me unable to copy and modify it.

Currently I'm embedding the source code of pdfbox to allow me to modify the
above classes, I believe it would be definitely better if you can
officially add an insert point or some hooks to them.

Thank you.

Re: Feature request for filtering TextPosition in PDFTextStripperByArea and PDFTextStripper

[Tilman Hausherr <TH...@t-online.de>]

I think I did something similar in 2018 that you might use, see the 
FilteredTextStripper class in ExtractText.java . That one only extracts 
text with angle 0.


/**
  * TextStripper that only processes glyphs that have angle 0.
  */
class FilteredTextStripper extends PDFTextStripper
{
     FilteredTextStripper() throws IOException
     {
     }

     @Override
     protected void processTextPosition(TextPosition text)
     {
         int angle = ExtractText.getAngle(text);
         if (angle == 0)
         {
             super.processTextPosition(text);
         }
     }
}



     static int getAngle(TextPosition text)
     {
         // should this become a part of TextPosition?
         Matrix m = text.getTextMatrix().clone();
         m.concatenate(text.getFont().getFontMatrix());
         return (int) 
Math.round(Math.toDegrees(Math.atan2(m.getShearY(), m.getScaleY())));
     }


Tilman


On 05.03.2024 11:52, Hengyu Weng wrote:
> Sometimes the watermark will overlap with normal text which we want to
> extract, so it would be great if it is possible to insert a filter and skip
> some useless TextPositons (e.g. the text of the watermark may have a
> rotation). I think the 'writePage' method in 'PDFTextStripper' is an
> appropriate place to add this filter, but I found it is difficult to
> override this method as it refers to a lot of private members, and
> PDFTextStripper extends LegacyPDFStreamEngine, which is a non-public class,
> which makes me unable to copy and modify it.
>
> Currently I'm embedding the source code of pdfbox to allow me to modify the
> above classes, I believe it would be definitely better if you can
> officially add an insert point or some hooks to them.
>
> Thank you.
>


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