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Image Quality Reduces when Merging Multiple Presentation Files


We have an issue with the quality of image output while merging the multiple power point files.
We have replicated the issue in a sample project and attached the sample project here.
AsposeSlides-SampleProject-MergeFiles-Issue.zip (98.4 KB).

Also, Please find the respective attached PPTX files used for merging here
Files To Merge.zip (127.8 KB)

You need to put all the above files in a folder and map it’s path in the sample project.
MergeIssueForm.cs => Line Number => 18. (variable name appDir)

After that if you run the project and click on the “Merge PPT Files” button. You will get the merged file in the same folder (appDir). Now if you open and look at the output , the image quality is very low. (You can check the “Asset Growth” header text in 2nd Slide).

So this is the issue we are getting, only when we are merging all the four files that we have provided to you. But if you just exclude the first file named “1-SectionReport.pptx” when you are merging the file, then we don’t see this issue.. This looks very weird to us and not sure why it is happening.

Also, we have attached a screenshot of both the ppt output’s and you can review the quality difference here.
Merged all four files-Issue-Seen.png (105.1 KB)
Excluded 1st file for merging-No Issue.png (116.7 KB)

Please review and provide us a solution as soon as you can.

Thanks in Advance,

Thank you for the issue description. I reproduced the problem with reducing the image quality and logged the issue with ID SLIDESNET-42802 in our tracking system. Our development team will investigate this case. You will be notified when the problem is fixed.

Any update on this issue?


I requested an update on this issue from our development team. I will let you know soon.

The issue has been scheduled for investigation on 2021/41 week.

Thank you for the update.

I believe that should be third week of October 2021. Please let us know otherwise.


Yes, you are right. Thank you for your patience.

Our development team investigated the issue. This behavior does not relate to Aspose.Slides API but is specific to PowerPoint. You can verify this by following these steps:

  1. Open “1-SectionReport.pptx” file in PowerPoint first.
  2. Open “360939–1.pptx” file in PowerPoint.
  3. Copy the slide from “360939–1.pptx” to “1-SectionReport.pptx” and save the result as “result.pptx”.
  4. Close all presentations.
  5. Open “result.pptx” in PowerPoint.

result.png (123.2 KB)

Thanks for the update.

Is there anything or any work-around that you can think of ,that we can add before we generate the pptx via code to avoid this issue?

Please let us know.


As you rightly noted, the merging works fine without the first file. If you have a possibility to differ such presentations according to content, you can try to merge the presentations with images first and then the rest of them.