Add test to ensure correct texture rendering

osu.Framework.Tests/Visual/Graphics/TestSceneTexturePremultiplication.cs

@@ -0,0 +1,128 @@
+// Copyright (c) ppy Pty Ltd <[email protected]>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.Collections.Generic;
+using System.IO;
+using System.Threading;
+using System.Threading.Tasks;
+using NUnit.Framework;
+using osu.Framework.Allocation;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics.Shapes;
+using osu.Framework.Graphics.Sprites;
+using osu.Framework.Graphics.Textures;
+using osu.Framework.IO.Stores;
+using osu.Framework.Platform;
+using osuTK;
+using osuTK.Graphics;
+using SixLabors.ImageSharp;
+using SixLabors.ImageSharp.PixelFormats;
+
+namespace osu.Framework.Tests.Visual.Graphics
+{
+    public partial class TestSceneTexturePremultiplication : FrameworkTestScene
+    {
+        private TextureStore textures = null!;
+
+        [BackgroundDependencyLoader]
+        private void load(GameHost host)
+        {
+            textures = new TextureStore(host.Renderer, host.CreateTextureLoaderStore(new CustomResourceStore()), false, TextureFilteringMode.Nearest);
+        }
+
+        [Test]
+        public void TestComparison()
+        {
+            AddStep("setup", () =>
+            {
+                Child = new FillFlowContainer
+                {
+                    Anchor = Anchor.Centre,
+                    Origin = Anchor.Centre,
+                    AutoSizeAxes = Axes.Both,
+                    Spacing = new Vector2(0f, 5f),
+                    Direction = FillDirection.Vertical,
+                    Children = new Drawable[]
+                    {
+                        new Container
+                        {
+                            AutoSizeAxes = Axes.Both,
+                            Children = new[]
+                            {
+                                new Box
+                                {
+                                    Size = new Vector2(256, 128),
+                                    Colour = Color4.Blue,
+                                },
+                                new Sprite
+                                {
+                                    Texture = textures.Get("zero-to-red"),
+                                    Size = new Vector2(256, 128),
+                                }
+                            },
+                        },
+                        new SpriteText
+                        {
+                            Text = "Rendering of the sprite above should be identical to the one below",
+                        },
+                        new Sprite
+                        {
+                            Texture = textures.Get("blue-to-red"),
+                            Size = new Vector2(256, 128),
+                        },
+                    }
+                };
+            });
+        }
+
+        private class CustomResourceStore : IResourceStore<byte[]>
+        {
+            public byte[] Get(string name) => throw new System.NotImplementedException();
+            public Task<byte[]> GetAsync(string name, CancellationToken cancellationToken = default) => throw new System.NotImplementedException();
+
+            public Stream GetStream(string name)
+            {
+                switch (name)
+                {
+                    case "zero-to-red":
+                    {
+                        var memoryStream = new MemoryStream();
+
+                        Image<Rgba32> image = new Image<Rgba32>(256, 1);
+
+                        for (int i = 0; i < 256; i++)
+                            image[i, 0] = new Rgba32(255, 0, 0, (byte)i);
+
+                        image.SaveAsPng(memoryStream);
+                        memoryStream.Seek(0, SeekOrigin.Begin);
+                        return memoryStream;
+                    }
+
+                    case "blue-to-red":
+                    {
+                        var memoryStream = new MemoryStream();
+
+                        Image<Rgba32> image = new Image<Rgba32>(256, 1);
+
+                        for (int i = 0; i < 256; i++)
+                            image[i, 0] = new Rgba32((byte)i, 0, (byte)(255 - i), 255);
+
+                        image.SaveAsPng(memoryStream);
+                        memoryStream.Seek(0, SeekOrigin.Begin);
+                        return memoryStream;
+                    }
+
+                    default:
+                        return Stream.Null;
+                }
+            }
+
+            public IEnumerable<string> GetAvailableResources() => new[] { "zero-to-red", "blue-to-red" };
+
+            public void Dispose()
+            {
+            }
+        }
+    }
+}