Scene compositor (TASK 4 ship step 1): encoder master-frame scaffolding

Software compositor that renders a scene into the encoder's master VideoFrame, mirroring the XAML preview minus editing chrome: backdrop -> background -> elements (UniformToFill cover-crop, round clip, mirror, opacity, border) -> branding flash. NOTE FOR USERS: this change shows NO difference in the app's UI — it is pure backend scaffolding laying the groundwork for live video capture/streaming. The preview you see is unchanged. - Services/Compositor/: SceneCompositor (Render(scene, frameFor resolver, flashFrame, CompositorOptions)), CompositorOptions (source rect + output size; 16:9 full master, vertical 607x1080 -> 1080x1920), StretchMath (pure UniformToFill + bilinear), StaticPixelCache (asset bytes -> BGRA8 frame) - Frame sources injected via Func<SceneElement, VideoFrame?> resolver, so the compositor is pure, WPF-free, and hermetic to test (D3D11 upgrade behind the same seam later) - SceneElement.TryGetBorderColor public (shared hex parse), stale MainViewModel comment fixed, pre-existing CS1998 in YouTubeAuthServiceTests cleaned up - Tests: SceneCompositorTests integration (full scene + vertical tier + flash) + StretchMath units, docs updated (72 tests passing, 0 warnings)
2026-08-10 10:15:58 -07:00
parent b00a4cbd5e
commit 18a21010bb
11 changed files with 681 additions and 11 deletions
@@ -0,0 +1,48 @@
+using System.IO;
+using System.Windows.Media;
+using System.Windows.Media.Imaging;
+
+namespace ytLive.Services.Compositor;
+
+/// <summary>
+/// Decodes a layout asset's bytes into a tightly-packed BGRA8 <see cref="VideoFrame"/>
+/// once per content-hash asset id. The preview uses the WPF <c>BitmapImage</c> in
+/// ImageCache; the output path needs raw pixels, so assets decode here instead.
+/// </summary>
+public static class StaticPixelCache
+{
+    private static readonly Dictionary<string, VideoFrame> Cache = new(StringComparer.Ordinal);
+
+    public static VideoFrame? Get(string assetId)
+    {
+        if (string.IsNullOrWhiteSpace(assetId)) return null;
+        if (Cache.TryGetValue(assetId, out var frame)) return frame;
+
+        var bytes = LayoutStore.Instance?.GetAssetBytes(assetId);
+        if (bytes == null || bytes.Length == 0) return null;
+
+        var decoded = Decode(bytes);
+        if (decoded != null) Cache[assetId] = decoded;
+        return decoded;
+    }
+
+    public static VideoFrame? Decode(byte[] bytes)
+    {
+        try
+        {
+            using var stream = new MemoryStream(bytes, writable: false);
+            var decoder = BitmapDecoder.Create(stream, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.OnLoad);
+            var source = decoder.Frames[0];
+            var bgra = new FormatConvertedBitmap(source, PixelFormats.Bgra32, null, 0);
+            var width = bgra.PixelWidth;
+            var height = bgra.PixelHeight;
+            var pixels = new byte[width * height * 4];
+            bgra.CopyPixels(pixels, width * 4, 0);
+            return new VideoFrame(width, height, pixels);
+        }
+        catch
+        {
+            return null;
+        }
+    }
+}