Enhance Scanned Pages works very slowly

[Eymann]

Recently, our employees noticed that when they wanted to optimize several PDF or JEPG files with the “Enhance Scanned Pages” tool, it was very slow or did not finish optimizing at all.

We then tested different scans with different data sizes and looked at the times.
What surprised us was...

Map1 (600 KB) took 20 seconds.
Map2 (2,400 KB) took 5 minutes.
Map3 (3,300 KB) took 30 minutes if you were lucky, or it went into an endless loop.

We tested it on different versions of PDF XChange.
On version 10.5.1 build 394 on Win10 and Win11
On version 10.8.4 build 409 on Win10 and Win11 (latest)

We also disabled the virus scanner to rule this out.

But in all tests with the various scenarios, the optimization was very slow or did not run at all.

I know that this tool, “Enhance Scanned Pages,” used to work very quickly, completing the optimization successfully within a few minutes (if not seconds), depending on the data size.
But the fact that it already fails with a 3.5 MB JEPG file means that something is wrong!

I have taken a screenshot of the settings we use, see attachment.
We cannot change the settings; we have to submit the plans to the authorities with these compression settings.

I have also attached the scans with the different data sizes as a zip file so you can test it yourself.

If you need more information or details, please feel free to ask me.

Enhance Scanned Pages Settings.png

Map1-3.zip

[Daniel - PDF-XChange]

Hello, Eymann

The good news is, I was able to reproduce the issue and narrow it down to something in the indexed compression options, most likely LZW specifically.
I have already shown the Dev team, and we created the following ticket to investigate the error and try to find a solution.

RT#7779: Bug: Very slow LZW compression actions.

I cannot promise a timeline for a resolution, but hopefully it will not be too long. Keep an eye out for updates in the meantime.

Kind regards,

[Eymann]

Hello Daniel

Thank you very much for taking on this problem.

For your information, I tested it on all different indexed (ZIP, Run Length, and LZW), and it was equally fast or slow with all variants.
So it's not just down to LZW.

Kind regards

image.png

[Sean - PDF-XChange]

Hi Eymann,

Thanks for that additional information - the team will get to this in due course.

Kind regards,