can I upgrade directly from High Sierra to Ventura OS on my Imac

Technically, if this computer Qualifies to run macOS 13 Ventura - Yes

Though, would be more prudent and take it in Steps versus the " Leap Of Faith " all goes well.

Much has changes since the release of High Sierra in 2017

For one, the Drive Format from possible the older HFS Journaled / GUID to the APFS / GUID.

Plus there maybe some EFI BOOT ROMS along the eventual journey to Final Destination of Ventura

The Age of this computer will Govern what newer version of macOS it will Qualify to install. Use About this Mac from the Apple Icon on Desktop - the required Information will be there.

With the above information in-hand - follow this How to get old versions of macOS and verify what version this computer Qualifies to install.  For Best results use Safari to commence the download as Others may not work.

Safari will open a redirect and open the Apple Store where the download can commence.

Does this computer appear as Listed and qualifying for an upGrade to a newer version of macOS? 

The below links will help identify which version of macOS  this computer may Qualify to run.

Computer Qualifying for macOS 13 Ventura 

Computer Qualify for the Monterey upgrade

macOS Big Sur 11 hardware requirements

macOS Catalina 10.15 hardware requirements

macOS Mojave 10.14 hardware requirements

Make Time Machine Backup  is very useful 

Notation - Mojave is the Last version to support 32 bit applications / extensions and Drivers. Catalina, Big Sur, Monterey, Ventura supports only 64 bit and there is no workaround.

Suggest using Go64 to find 32 bit application before attempting the upGrade. Some or many of the Application already installed may require an update or upGrades to 64 Bit Version

You can update to macOS Ventura from macOS High Sierra using the App Store page: macOS Ventura - Mac App Store

Before upgrading, make sure your iMac is compatible with macOS Ventura. From the Apple menu () in the menu bar, select About This Mac.

• If your iMac was introduced in 2017 or later, you can upgrade to macOS Ventura.
• If your iMac was introduced in 2015, you can upgrade to macOS Monterey.
• If your iMac was introduced in 2014, you can upgrade to macOS Big Sur.
• If your iMac was introduced in 2012 or 2013, you can upgrade to macOS Catalina.
• If your iMac was introduced between 2009 and 2011, you can't upgrade past macOS High Sierra.

Before upgrading to a new version of macOS, it's a good idea to make a backup of your Mac with Time Machine and make sure you have enough storage available, ideally at least 60 GB.

Back up your Mac with Time Machine - Apple Support

Free up storage space on your Mac - Apple Support