iTextSharp ShowTextAligned Anchor Point

Question

I'm currently successfully adding text to a PDF using iTextSharp's ShowTextAligned method. The method looks like this (C#):

public void ShowTextAligned(
    int alignment,
    string text,
    float x,
    float y,
    float rotation
)

However, it is unclear where the anchor point is for the text we're making. We provide x and y, but does these correspond to the upper left corner of the text rectangle, the lower left corner, or something else? Also is this impacted by line spacing?

I looked at the documentation at this website, but it isn't very explanatory. See PdfContentByte Class / PdfContentByte Methods / ShowTextAligned Method.

See [this question](http://stackoverflow.com/q/30319228/231316) which explains PDF coordinate systems. The short answer is that in most simple PDF the x,y is relative to the lower left corner. — Chris Haas, Feb 08 '16 at 23:20

score 11 · Accepted Answer · answered Feb 09 '16 at 07:04

Obviously the anchor point depends on the kind of alignment. It does not make sense to say you right-align if your anchor point is at the left side of the text.

Furthermore, text operations usually align relative to the baseline.

Thus:

For left aligned text the anchor point is the left-most point of the text baseline.
For center aligned text the anchor point is the middle point of the text baseline.
For right aligned text the anchor point is the right-most point of the text baseline.

More visually:

This has been generated using:

[Test]
public void ShowAnchorPoints()
{
    Directory.CreateDirectory(@"C:\Temp\test-results\content\");
    string dest = @"C:\Temp\test-results\content\showAnchorPoints.pdf";

    using (Document document = new Document())
    {
        PdfWriter writer = PdfWriter.GetInstance(document, new FileStream(dest, FileMode.Create, FileAccess.Write));
        document.Open();

        PdfContentByte canvas = writer.DirectContent;

        canvas.MoveTo(300, 100);
        canvas.LineTo(300, 700);
        canvas.MoveTo(100, 300);
        canvas.LineTo(500, 300);
        canvas.MoveTo(100, 400);
        canvas.LineTo(500, 400);
        canvas.MoveTo(100, 500);
        canvas.LineTo(500, 500);
        canvas.Stroke();

        ColumnText.ShowTextAligned(canvas, Element.ALIGN_LEFT, new Phrase("Left aligned"), 300, 500, 0);
        ColumnText.ShowTextAligned(canvas, Element.ALIGN_CENTER, new Phrase("Center aligned"), 300, 400, 0);
        ColumnText.ShowTextAligned(canvas, Element.ALIGN_RIGHT, new Phrase("Right aligned"), 300, 300, 0);
    }
}

iTextSharp ShowTextAligned Anchor Point

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