The type or namespace name 'Graphics' does not exist in the namespace 'Microsoft'

[zipswich]

If I update the NuGet package Microsoft.Toolkit.Uwp.UI.Animations to any 7.x version for the sample app Photo Lab, I get the following errors:

1>------ Build started: Project: PhotoLab, Configuration: Debug x64 ------
1>E:\VS Solutions\PhotoLab\PhotoLab\DetailPage.xaml.cs(25,17,25,25): error CS0234: The type or namespace name 'Graphics' does not exist in the namespace 'Microsoft' (are you missing an assembly reference?)
1>E:\VS Solutions\PhotoLab\PhotoLab\LoadedImageBrush.cs(1,17,1,25): error CS0234: The type or namespace name 'Graphics' does not exist in the namespace 'Microsoft' (are you missing an assembly reference?)
1>E:\VS Solutions\PhotoLab\PhotoLab\LoadedImageBrush.cs(2,17,2,25): error CS0234: The type or namespace name 'Graphics' does not exist in the namespace 'Microsoft' (are you missing an assembly reference?)
1>E:\VS Solutions\PhotoLab\PhotoLab\LoadedImageBrush.cs(3,17,3,25): error CS0234: The type or namespace name 'Graphics' does not exist in the namespace 'Microsoft' (are you missing an assembly reference?)
1>E:\VS Solutions\PhotoLab\PhotoLab\LoadedImageBrush.cs(29,16,29,28): error CS0246: The type or namespace name 'ICanvasImage' could not be found (are you missing a using directive or an assembly reference?)
1>E:\VS Solutions\PhotoLab\PhotoLab\LoadedImageBrush.cs(43,31,43,43): error CS0246: The type or namespace name 'ICanvasImage' could not be found (are you missing a using directive or an assembly reference?)
1>E:\VS Solutions\PhotoLab\PhotoLab\LoadedImageBrush.cs(23,9,23,23): error CS0246: The type or namespace name 'ContrastEffect' could not be found (are you missing a using directive or an assembly reference?)
1>E:\VS Solutions\PhotoLab\PhotoLab\LoadedImageBrush.cs(24,9,24,23): error CS0246: The type or namespace name 'ExposureEffect' could not be found (are you missing a using directive or an assembly reference?)
1>E:\VS Solutions\PhotoLab\PhotoLab\LoadedImageBrush.cs(25,9,25,33): error CS0246: The type or namespace name 'TemperatureAndTintEffect' could not be found (are you missing a using directive or an assembly reference?)
1>E:\VS Solutions\PhotoLab\PhotoLab\LoadedImageBrush.cs(26,9,26,27): error CS0246: The type or namespace name 'GaussianBlurEffect' could not be found (are you missing a using directive or an assembly reference?)
1>E:\VS Solutions\PhotoLab\PhotoLab\LoadedImageBrush.cs(27,9,27,25): error CS0246: The type or namespace name 'SaturationEffect' could not be found (are you missing a using directive or an assembly reference?)
1>C:\Program Files (x86)\Windows Kits\10\bin\10.0.19041.0\XamlCompiler\Microsoft.Windows.UI.Xaml.Common.targets(486,5): error MSB4181: The "CompileXaml" task returned false but did not log an error.

I thought I must have missed something very simple and obvious but I could not find a clue after an extensive search. Could anyone offer a tip?