Add COLRv1 paint tree renderer, switch to SharpAstro.FreeType 3.2.13

COLRv1 color emoji rendering via paint tree walking:
- PaintColrLayers, PaintGlyph, PaintSolid, PaintColrGlyph, PaintComposite
- Radial gradient with color stop interpolation and coordinate scaling
- Affine transforms via System.Numerics.Matrix3x2 (compose, inverse for gradients)
- Tested with Noto COLRv1 emoji and BabelStone Xiangqi COLR v0

Also: RGBAColor32.Lerp/WithAlpha, RgbaImage.BlendPixelAt, 30 tests total.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: sebgod

.github/workflows/dotnet.yml

@@ -7,7 +7,7 @@ on:
     branches: [ main ]
 
 env:
-  VERSION_PREFIX: 1.2.${{ github.run_number }}
+  VERSION_PREFIX: 1.3.${{ github.run_number }}
   VERSION_REV: ${{ github.run_attempt }}
   VERSION_HASH: +${{ github.sha }}
   BUILD_CONF: Release

src/DIR.Lib.Tests/Baselines/color_noto_emoji.bmp

@@ -0,0 +1,70 @@
+using Shouldly;
+
+namespace DIR.Lib.Tests;
+
+public class RGBAColor32Tests
+{
+    [Fact]
+    public void Lerp_AtZero_ReturnsFirst()
+    {
+        var a = new RGBAColor32(255, 0, 0, 255);
+        var b = new RGBAColor32(0, 0, 255, 255);
+        RGBAColor32.Lerp(a, b, 0f).ShouldBe(a);
+    }
+
+    [Fact]
+    public void Lerp_AtOne_ReturnsSecond()
+    {
+        var a = new RGBAColor32(255, 0, 0, 255);
+        var b = new RGBAColor32(0, 0, 255, 255);
+        RGBAColor32.Lerp(a, b, 1f).ShouldBe(b);
+    }
+
+    [Fact]
+    public void Lerp_AtHalf_ReturnsMidpoint()
+    {
+        var a = new RGBAColor32(0, 0, 0, 255);
+        var b = new RGBAColor32(200, 100, 50, 255);
+        var mid = RGBAColor32.Lerp(a, b, 0.5f);
+        mid.Red.ShouldBe((byte)100);
+        mid.Green.ShouldBe((byte)50);
+        mid.Blue.ShouldBe((byte)25);
+        mid.Alpha.ShouldBe((byte)255);
+    }
+
+    [Fact]
+    public void WithAlpha_FullMask_PreservesAlpha()
+    {
+        var color = new RGBAColor32(255, 0, 0, 200);
+        var result = color.WithAlpha(255);
+        result.Alpha.ShouldBe((byte)200);
+        result.Red.ShouldBe((byte)255);
+    }
+
+    [Fact]
+    public void WithAlpha_HalfMask_HalvesAlpha()
+    {
+        var color = new RGBAColor32(255, 0, 0, 255);
+        var result = color.WithAlpha(128);
+        result.Alpha.ShouldBeInRange((byte)127, (byte)129);
+    }
+
+    [Fact]
+    public void WithAlpha_ZeroMask_ReturnsZeroAlpha()
+    {
+        var color = new RGBAColor32(255, 0, 0, 255);
+        color.WithAlpha(0).Alpha.ShouldBe((byte)0);
+    }
+
+    [Fact]
+    public void Luminance_White()
+    {
+        new RGBAColor32(255, 255, 255, 255).Luminance.ShouldBe((byte)255);
+    }
+
+    [Fact]
+    public void Luminance_Black()
+    {
+        new RGBAColor32(0, 0, 0, 255).Luminance.ShouldBe((byte)0);
+    }
+}

src/DIR.Lib.Tests/Baselines/color_xiangqi.bmp

@@ -100,6 +100,51 @@ public void ColorGlyph_IsColored_Flag()
         glyph.IsColored.ShouldBeTrue("Xiangqi glyph should be a color glyph");
     }
 
+    [Fact]
+    public void RenderColorGlyphs_NotoEmoji()
+    {
+        var emojiFont = Path.Combine(AppContext.BaseDirectory, "Fonts", "Noto-COLRv1.ttf");
+        if (!File.Exists(emojiFont))
+            return;
+
+        var img = CreateGridImage(300, 80, gridSpacing: 20);
+
+        // 😀🎉🌍🔥 — common emoji
+        RenderColorText(img, "\U0001F600\U0001F389\U0001F30D\U0001F525", emojiFont, 48f, 10, 5);
+
+        CompareBaseline(img, "color_noto_emoji.bmp");
+    }
+
+    [Fact]
+    public void ColorGlyph_NotoEmoji_IsColored()
+    {
+        var emojiFont = Path.Combine(AppContext.BaseDirectory, "Fonts", "Noto-COLRv1.ttf");
+        if (!File.Exists(emojiFont))
+            return;
+
+        var glyph = _rasterizer.RasterizeGlyph(emojiFont, 48f, new Rune(0x1F600)); // 😀
+        glyph.Width.ShouldBeGreaterThan(0);
+        glyph.IsColored.ShouldBeTrue("Noto COLRv1 emoji should be a color glyph");
+    }
+
+    [Fact]
+    public void RenderText_ChessPieces()
+    {
+        var meridaFont = Path.Combine(AppContext.BaseDirectory, "Fonts", "Merida.ttf");
+        if (!File.Exists(meridaFont))
+            return;
+
+        var img = CreateGridImage(400, 80, gridSpacing: 20);
+
+        // Chess pieces: ♔♕♖♗♘♙ (white) ♚♛♜♝♞♟ (black)
+        RenderText(img, "\u2654\u2655\u2656\u2657\u2658\u2659", meridaFont, 48f,
+            new RGBAColor32(255, 255, 255, 255), 10, 5);
+        RenderText(img, "\u265A\u265B\u265C\u265D\u265E\u265F", meridaFont, 48f,
+            new RGBAColor32(40, 40, 40, 255), 10, 40);
+
+        CompareBaseline(img, "text_chess_pieces.bmp");
+    }
+
     [Fact]
     public void GrayscaleGlyph_IsNotColored()
     {

src/DIR.Lib.Tests/Baselines/text_chess_pieces.bmp

@@ -130,6 +130,42 @@ public void BlitRgba_TransparentPixelsPreserveBackground()
         GetPixel(img, 1, 0).ShouldBe(bg); // unchanged
     }
 
+    [Fact]
+    public void BlendPixelAt_OpaqueOnBlack()
+    {
+        var img = new RgbaImage(4, 4);
+        img.Clear(new RGBAColor32(0, 0, 0, 255));
+        var red = new RGBAColor32(255, 0, 0, 255);
+
+        img.BlendPixelAt(1, 1, red);
+
+        GetPixel(img, 1, 1).ShouldBe(red);
+    }
+
+    [Fact]
+    public void BlendPixelAt_SemiTransparent()
+    {
+        var img = new RgbaImage(2, 2);
+        img.Clear(new RGBAColor32(0, 0, 255, 255)); // blue
+        var semiRed = new RGBAColor32(255, 0, 0, 128);
+
+        img.BlendPixelAt(0, 0, semiRed);
+
+        var pixel = GetPixel(img, 0, 0);
+        pixel.Red.ShouldBeGreaterThan((byte)0);
+        pixel.Blue.ShouldBeGreaterThan((byte)0);
+        pixel.Alpha.ShouldBe((byte)255);
+    }
+
+    [Fact]
+    public void BlendPixelAt_OutOfBounds_NoThrow()
+    {
+        var img = new RgbaImage(2, 2);
+        img.BlendPixelAt(-1, 0, new RGBAColor32(255, 0, 0, 255));
+        img.BlendPixelAt(0, 5, new RGBAColor32(255, 0, 0, 255));
+        // Should not throw
+    }
+
     [Fact]
     public void Resize_AllocatesNewBuffer()
     {