PDFsharp & MigraDoc Foundation

PDFsharp - A .NET library for processing PDF & MigraDoc Foundation - Creating documents on the fly
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PostPosted: Fri Nov 05, 2021 1:27 am 

Joined: Fri Nov 05, 2021 1:14 am
Posts: 1
I've got an app which finds text in a PDF document, then tries to put an image over it.
While looking for the text, I'm finding the relevant operators/matrices. For an example document, I get:

0.75 0 0 -0.75 0 841.920044 cm
1 0 0 -1 49.119999 304.799988 Tm

But I've got issues positioning the image correctly from that.
From the calculation, it looks like I should be putting the image at {36.83999925,613.320053}

But PdfSharp does the positioning differently, so I'm not sure how to translate that.
I tried to apply the scale, translate, scale and use the original Tm numbers:
gfx.ScaleTransform(0.75, -0.75);
gfx.TranslateTransform(0, 841.920044);
gfx.ScaleTransform(1, -1);
  signatureLocation.Value.X, signatureLocation.Value.Y,
  90, 90 / signatureImg.PointWidth * signatureImg.PointHeight);

But that doesn't work quite the way I expected :(

How do I translate the cm/Tm numbers to DrawImage at the exact point?

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PostPosted: Fri Nov 05, 2021 10:42 am 
PDFsharp Expert
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Joined: Sat Mar 14, 2015 10:15 am
Posts: 683
Location: CCAA
Already discussed here:

Not much we can do without having the PDF files.

Maybe you have to call "WorldToDefaultPage" or some other conversion method.
var pdfPosition = _gfx.Transformer.WorldToDefaultPage(destinationPosition);

With Adobe Reader you can measure the position of the text on the page and then use PDFsharp to draw at the location you measured.
Comparing the measured position from Adobe Reader with the numbers given in the PDF should allow you to determine a formula when you do it for several documents.

Best regards
(Freelance Software Developer with several years of MigraDoc/PDFsharp experience)

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