I use Ellipse object in PRPT to build circle. I do width=30 and height=30.
When previewing in eg. PDF the circle looks fine. However, when I preview in HTML some pixels at the bottom and right side get missing.
Doing width=60 and height=60 looks fine.
See the screencast for the reference: https://pentaho.viewscreencasts.com/embed/eb37f309e5584eea913311af7ed51ac5