fix intermittent watermark opacity (#2523)

CHANGELOG.md

@@ -26,6 +26,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Fix NVIDIA startup errors on arm64
 - Fix remote stream durations in playouts created using block, sequential or scripted schedules
 - Fix playback troubleshooting selecting a subtitle even with no subtitle stream selected in the UI
+- Fix intermittent watermark opacity
 
 ### Changed
 - Do not use graphics engine for single, permanent watermark

ErsatzTV.Infrastructure/Streaming/Graphics/Image/WatermarkElement.cs

@@ -45,7 +45,7 @@ public class WatermarkElement : ImageElementBase
                                 0
                             )
                         )
-                    )";
+                    ) * {_watermark.Opacity / 100.0f}";
                 _maybeOpacityExpression = new Expression(expressionString);
             }
             else if (_watermark.Mode is ChannelWatermarkMode.OpacityExpression &&