The current version of the module makes use of the online service https://compressor.io to shrink the images.
- Ensure that Sitecore PowerShell Extensions 5.0 or later is installed.
- Install the Image Optimizer package found in the repo.
- Profit!
The module provides two ways to optimize. The first is through the context menu while selecting an image. The second can through a report, which supports filtering by media size.
The following are included with SPE 5.0 and should be used to help aid finding large images.
I found inspiration for this from Dylan McCurry. Check out his post here.