How to obtain the size of the camera preview stream

[nihaoyahaha]

The current requirement is to limit the movement range of the green backboard within the camera preview stream area,Inside the red border in the following image, and I am unable to obtain the actual size of the camera preview stream

Environment

• .NET MAUI CommunityToolkit.Maui:9.1.1
• .NET MAUI CommunityToolkit.Maui.Camera: 2.0.0
• OS: WINDOWS 10.0.17763.0
• .NET MAUI: 9.0.22