PDF file size is different between versions


#1

Hi,

I’m investigating file size changes when exporting a PPTX file to PDF.

My code is simply this:
var pres = new Presentation(fileName);
pres.Save(root + “\Pres.pdf”, SaveFormat.Pdf);

I’ve done some tests using different presentations using different presentations to see how the produced PDF file changed.

Using the attached presentation I have something like this:

  • Aspose.Slides 17.4: 1.9 MB
  • Aspose.Slides 19.1: 17.5 MB
  • Aspose.Slides 19.5: 9.5 MB

(Produced files are attached)

Using a presentation from one of our customer (unfortunately I cannot share it), using the same code, I have this results:

  • Aspose.Slides 17.4: 2 MB
  • Aspose.Slides 19.1: 15.2 MB
  • Aspose.Slides 19.5: 15.3 MB

In other tests Aspose.Slides 19.5 gave even more large files compared with 19.1.

How can we explain these differences? In particular from 17.4 to recent versions.

Thanks
Pres.zip (7.7 MB)


#2

Pres-sample-17.4.pdf (1.9 MB)
Pres-sample-19.5.pdf (9.3 MB)


#3

@andreagasparin,

I have worked with the sample file shared by you. An issue with ID SLIDESNET-41218 has been created in our issue tracking system to further investigate and resolve the issue. We will share good news with you soon.


#4

Hi @Adnan.Ahmad,

We would like to raise the priority of this issue, is it possibile? Or do I need to create a new one under the paid support forum?

thanks


#5

@andreagasparin,

Thanks for contacting us. I like to inform that we have number of options to adjust desired images quality in generated PDF. Using them the PDF size can be decreased. Please check following sample code.

using (Presentation pres = new Presentation(“pres.pptx”))
{
pres.Save(“pres.pdf”, SaveFormat.Pdf, new PdfOptions
{
BestImagesCompressionRatio = true,
SufficientResolution = 64,
JpegQuality = 95
});
}

Please let us know if this solution satisfy you.


#6

We already use those properties but here we are not touching them because we want the output presentation to be in high quality, so this is not an option for us.

Did you managed to convert the issue to a priority issue?

Thanks and best regards


#7

@andreagasparin,

If you have paid support subscription then you can log a ticket in Paid Support help desk separately.


#8

Ok, I’ve opened a new ticket in the paid support forum, thanks


#9

@andreagasparin,

Thank you for sharing the feedback.


#10

@andreagasparin,

I like to inform that we have investigated this issue in details and i like to share our findings with you. Files can be downloaded from this link.

  • Sample presentation contains several big images. File size increasing is a result of output images quality improvement added to Aspose.Slides 18.6 release. If you compare images on the first page of Pres.18.5-out.pdf and Pres.19.9-out.pdf it is easy to notice, that Slides 18.5 release output has blurry image opposite to sharp and high-quality one in 19.9 output even with 300% and more zoom in pdf.

  • To find a compromise between quality and file size, you could use PdfOptions.JpegQuality parameter as we suggested you earlier. Please compare Pres.19.9-out.pdf and Pres.19.9-out-JpegQuality50.pdf output files.

  • If you don’t want to use PdfOptions.JpegQuality parameter, it is possible for us to to control images resolution comparing to original presentation images. Check Pres.19.11-out-Resolution75.pdf output result.

  • Anyway the general principle with pdf containing images - the better image quality the bigger file size. We can’t significantly reduce output pdf file size for the sample presentation without affecting images quality.

  • Just to compare check Pres-PowerPoint2013-out.pdf file that shows how PowerPoint 2013 converts sample presentation to pdf. File size is small, but images are blurry.