Image Opacity in PdfSharp.NET

问题

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?

回答1:

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