Allow mask image to be supplied when calculating diff mask of two images

Author: stesee

.editorconfig

@@ -3,6 +3,9 @@
 # CA1303: Do not pass literals as localized parameters
 dotnet_diagnostic.CA1303.severity = none
 
+# CA2000: Dispose objects before losing scope
+dotnet_diagnostic.CA2000.severity = suggestion
+
 # var preferences
 csharp_style_var_elsewhere = true:warning
 csharp_style_var_for_built_in_types = true:warning