I'm using PDFSharp.NET library to watermark a list of PDFs file. Everything works fine, the website has a lot of samples.
http://www.pdfsharp.net/wiki/Graphics-sample.ashx
The last thing I need is to add the Company Logo, which is big, in the middle of the PDF Page.
I can use a PNG, so that areas which are set as transparent do not "cover" the PDF page".
The pdf is not generated using PDFSharp, but is an "Image" PDF.
For this reason, what I need, is, in addition to the transparency, which works, be able some how to set the Image Opacity!
The code to place the image is this one:
XGraphics gfx = XGraphics.FromPdfPage(page, XGraphicsPdfPageOptions.Append);
XImage image = XImage.FromFile(mypath);
gfx.DrawImage(image, pwidth/2-image.PixelWidth/2, pheight/2 image.PixelHeight/2);
gfx.Dispose();
Anyone has already faced with that?
I don't know how to alter the opacity of an image while drawing it using PDFsharp (and I'm afraid this can't be done).
So instead I would just open the logo (PNG) with an image processor and set the opacity there.
来源：https://stackoverflow.com/questions/16451008/image-opacity-in-pdfsharp-net