OpenCvSharp.Extensions' dependency on System.Drawing.Common uses version 8.0.6, while the nuspec file declares this dependency as version 7.0.0.
CS1705 Assembly 'OpenCvSharp.Extensions' with identity 'OpenCvSharp.Extensions, Version=1.0.0.0, Culture=neutral, PublicKeyToken=6adad1e807fea099' uses 'System.Drawing.Common, Version=8.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51' which has a higher version than referenced assembly 'System.Drawing.Common' with identity 'System.Drawing.Common, Version=7.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'
Summary of your issue
OpenCvSharp.Extensions' dependency on System.Drawing.Common uses version 8.0.6, while the nuspec file declares this dependency as version 7.0.0.
This prevents code to be build using .NET 7