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Use existing code, which assumes pixels, to draw a PDF?
http://forum.pdfsharp.de/viewtopic.php?f=2&t=1511		 Page 1 of 1
Author:  ddobrev [ Mon Jan 17, 2011 11:52 am ]
Post subject:  Use existing code, which assumes pixels, to draw a PDF?
Hi,

I have some code that draws a printing preview of a document. The document is drawn by an abstract class, DrawingProvider. It has a few methods for drawing (DrawString, DrawLine, etc.). I want to create a DrawingProvider, called DrawingProviderPDF. The data for the document, however, uses pixels, while PDF uses points. That's why in DrawingProviderPDF I apply the following code on each numeric value (coordinates or size) before using it (pdfGraphics is the XGraphics object I use to construct DrawingProviderPDF):

(pixels / pdfGraphics.Graphics.DpiX) * 72 - pixels / DPI (dots per inch) gives me the number of inches, and I multiply by 72 to get the number of points.

However, this doesn't work - the document is printed smaller, about two thirds of an A4 page on 120 DPI, and too large on 96 DPI. XGraphics.ScaleTransform(72 / pdfGraphics.Graphics.DpiX) didn't work as well. What am I doing wrong?

Project: PDFsharp
Build: GDI+
Version: 1.31
Author:  jeffhare [ Thu Jan 20, 2011 3:52 pm ]
Post subject:  Re: Use existing code, which assumes pixels, to draw a PDF?
Hmm. Shouldn't that simply be:

points = (pixels * 72) / (dpi of device where your # of pixels originated)

I think there are 72 points per inch. And since your code supplies the proper # of pixels at a given device resolution, you just need to plug in that device resolution to get to points.

I'm not an expert here but
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-Jeff
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