Hi!
Background
We have problems printing PDF files using an HP Indigo professional printer. The problems began when we started to use PDFSharp to merge a number of files into one, in a certain way. Before that we used Acrobat, but that was much slower and involved more steps than the newly written C# program that use PDFSharp.
The problem
The original pdf files have "Transparency blending Color Space" set to None. After loading and saving the PDF files with PDFSharp this setting (or perhaps lack of setting) is replaced with "DeviceRGB", which the printer (rip?) is not handling very well. It results in the CMYK 100% colours are no longer "clean", but consists of more colours. The output from the Indigo printer looks "dirty", due to the DeviceRGB setting.
I simplified the C# code to a minimum, just opening a document with PDFSharp and saving it. This still results in Transparency blend color space being set to DeviceRGB.
Code:
using PdfSharp.Pdf;
using PdfSharp.Pdf.IO;
namespace ConsoleApplication4
{
class Program
{
static void Main(string[] args) {
PdfDocument outputDocument = PdfReader.Open(@"C:\Old.pdf", PdfDocumentOpenMode.Modify);
outputDocument.Save(@"C:\Old_SavedByPDFSharp.pdf");
}
}
}
I'm using PDFSharp 1.50.3915.0.
What should we do to keep Transparency blending Color Space: None, just as it was in the original files?
This is what Acrobat Preflight output shows for a PDF that is correct (that is printing clean 100% colours on the Indigo printer):
Attachment:
Transparency blending.PNG [ 37.9 KiB | Viewed 10298 times ]
This is what the same setting looks like after saving the same file with PDFSharp:
Attachment:
pdfsharp.PNG [ 1.31 KiB | Viewed 10295 times ]
Thanks,
Andreas