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Editorial Team
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Asked: 2026-06-12T05:37:04+00:00

I’m working on a text extraction system from PDF files using iTextSharp. I have

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I’m working on a text extraction system from PDF files using iTextSharp. I have already created a class that implements ITextExtractionStrategy and implemented methods like RenderText(), GetResultantText() etc. I have studied LocationTextExtractionStrategy class provided by iTextSharp itself as well.

The problem I’m facing is that for a particular PDF document, the RenderText() method reports the horizontal position of a few text chunks incorrectly. This happens for around 15-20 chunks out of a total of 700+ text chunks available on the page. I’m using the following simple code to get text position in RenderText():

Vector curBaselineStart = renderInfo.GetBaseline().GetStartPoint();
LineSegment segment = renderInfo.GetBaseline();
TextChunk location = new TextChunk(renderInfo.GetText(), segment.GetStartPoint(), segment.GetEndPoint(), renderInfo.GetSingleSpaceWidth());
chunks.Add(location);

After collecting all the text chunks, I try to draw them on a bitmap, using Graphics class and the following simple loop:

for (int k = 0; k < chunks.Count; k++)
{
    var ch = chunks[k];
    g.DrawString(ch.text, fnt, Brushes.Black, ch.startLocation[Vector.I1], bmp.Height - ch.startLocation[Vector.I2], StringFormat.GenericTypographic);
}

The problem happens with the X (horizontal) dimension only for these few text chunks. They appear slightly towards the left than their actual position. Was wondering if there’s something wrong with my code here.

Shujaat

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1 Answer

  1. Editorial Team

    Finally figured this out. In PDF, computing actual text positions is more complicated than simply getting the baseline co-ordinates. You need to incorporate character and word spacing, horizontal and vertical scaling and some other factors too. I did some correspondance with iText guys and they have now incorporated a new method in TextRenderInfo class that provides actual character-by-character positions by taking care of all of the above factors.

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