App/Controllers/ImageController.cs

@@ -24,7 +24,7 @@ public static class ImageController
 
         await tileManager
             .CreateSection(dto)
-            .WriteToStream(response.Body, dto.OutputScale);
+            .DangerousWriteToPipe(response.BodyWriter, dto.OutputScale);
         
         await response.CompleteAsync();
     }
@@ -47,7 +47,7 @@ public static class ImageController
         var scale = float.Clamp(480f / int.Max(section.Width, section.Height), 0.01f, 1f);
         Console.WriteLine($"Generate random image for {coordinatePair} scale: {scale}");
         
-        await section.WriteToStream(response.Body, scale);
+        await section.DangerousWriteToPipe(response.BodyWriter, scale);
         await response.CompleteAsync();
     }
 }

App/StitchATon2.App.csproj

@@ -1,11 +1,12 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
     <PropertyGroup>
-        <TargetFramework>net8.0</TargetFramework>
+        <TargetFramework>net9.0</TargetFramework>
         <Nullable>enable</Nullable>
         <ImplicitUsings>enable</ImplicitUsings>
         <InvariantGlobalization>true</InvariantGlobalization>
         <RootNamespace>StitchATon2.App</RootNamespace>
+        <PublishAot>true</PublishAot>
     </PropertyGroup>
 
     <ItemGroup>

App/Utils.cs

@@ -1,3 +1,4 @@
+using System.IO.Pipelines;
 using StitchATon2.App.Models;
 using StitchATon2.Domain;
 using StitchATon2.Domain.ImageCreators;
@@ -19,4 +20,10 @@ public static class Utils
         var imageCreator = new ImageCreator(section);
         await imageCreator.WriteToStream(stream, scale!.Value);
     }
+
+    public static async Task DangerousWriteToPipe(this GridSection section, PipeWriter pipeWriter, float? scale)
+    {
+        var imageCreator = new DangerousImageCreator(section);
+        await imageCreator.WriteToPipe(pipeWriter, scale!.Value);
+    }
 }

Domain/ImageCreators/DangerousImageCreator.cs

@@ -0,0 +1,172 @@
+using System.IO.Pipelines;
+using System.Runtime.CompilerServices;
+using SixLabors.ImageSharp.PixelFormats;
+using StitchATon2.Infra;
+using StitchATon2.Infra.Buffers;
+using StitchATon2.Infra.Encoders;
+using StitchATon2.Infra.Synchronization;
+
+namespace StitchATon2.Domain.ImageCreators;
+
+public sealed class DangerousImageCreator : IDisposable
+{
+    private readonly GridSection _section;
+    private readonly IBuffer<Int32Pixel> _mmfReadBuffer;
+
+    private int FullWidth => _section.TileManager.Configuration.FullWidth;
+    private int FullHeight => _section.TileManager.Configuration.FullHeight;
+
+    private int OffsetX => _section.OffsetX;
+    private int OffsetY => _section.OffsetY;
+
+    private int Width => _section.Width;
+    private int Height => _section.Height;
+
+    private int TileWidth => _section.TileManager.Configuration.Width;
+    private int TileHeight => _section.TileManager.Configuration.Height;
+    private Tile TileOrigin => _section.Origin;
+    
+    private int RightmostPixelIndex => _section.TileManager.Configuration.RightTileIndex;
+    private int BottomPixelIndex => _section.TileManager.Configuration.BottomTileIndex;
+    
+    private TileManager TileManager => _section.TileManager;
+
+    public DangerousImageCreator(GridSection section)
+    {
+        _section = section;
+        _mmfReadBuffer = MemoryAllocator.Allocate<Int32Pixel>(TileWidth);
+    }
+    
+    ~DangerousImageCreator() => Dispose();
+
+    public async Task WriteToPipe(PipeWriter outputPipe, float scale, CancellationToken cancellationToken = default)
+    {
+        var scaleFactor = MathF.ReciprocalEstimate(scale);
+        var targetWidth = (int)(Width / scaleFactor);
+        var targetHeight = (int)(Height / scaleFactor);
+        
+        var encoder = new PngPipeEncoder(outputPipe, targetWidth, targetHeight);
+        encoder.WriteHeader();
+
+        var outputBufferSize = targetWidth * Unsafe.SizeOf<Rgb24>();
+
+        using var xLookup = Utils.BoundsMatrix(scaleFactor, targetWidth, FullWidth, OffsetX);
+        using var yLookup = Utils.BoundsMatrix(scaleFactor, targetHeight, FullHeight, OffsetY);
+
+        using var yStartMap = MemoryAllocator.Allocate<Int32Pixel>(targetWidth);
+        using var yEndMap = MemoryAllocator.Allocate<Int32Pixel>(targetWidth);
+        
+        var yStart = OffsetY;
+        
+        var outputTaskQueue = TaskHelper.SynchronizedTaskFactory.StartNew(() => { }, cancellationToken);
+        for (var y = 0; y < targetHeight; y++)
+        {
+            var yEnd = yLookup[y];
+            
+            var (localRow0, localOffsetY0) = int.DivRem(yStart, TileHeight);
+            MapRow(localRow0, localOffsetY0, xLookup, targetWidth, yStartMap);
+            
+            var (localRow1, localOffsetY1) = int.DivRem(yEnd, TileHeight);
+            MapRow(localRow1, localOffsetY1, xLookup, targetWidth, yEndMap);
+            
+            if (localRow0 != localRow1)
+            {
+                MapRow(localRow0, BottomPixelIndex, xLookup, targetWidth, yEndMap, true);
+            }
+            
+            int xStart = OffsetX, x0 = 0;
+
+            var pxInt32 = Int32Pixel.Zero;
+            ref var px = ref pxInt32;
+            ref var rChannel = ref Unsafe.As<Int32Pixel, byte>(ref px);
+            ref var gChannel = ref Unsafe.Add(ref rChannel, 4);
+            ref var bChannel = ref Unsafe.Add(ref rChannel, 8);
+            
+            var outputBuffer = MemoryAllocator.Allocate<byte>(outputBufferSize);
+            ref var outputChannel = ref outputBuffer.Span[0];
+            for (int x1 = 0; x1 < targetWidth; x1++)
+            {
+                var xEnd = xLookup[x1];
+
+                px = yEndMap[x1];
+                px += yStartMap[x0];
+                px -= yEndMap[x0];
+                px -= yStartMap[x1];
+                px /= Math.Max(1, (xEnd - xStart) * (yEnd - yStart));
+                
+                outputChannel = rChannel;
+                outputChannel = ref Unsafe.Add(ref outputChannel, 1);
+                
+                outputChannel = gChannel;
+                outputChannel = ref Unsafe.Add(ref outputChannel, 1);
+                
+                outputChannel = bChannel;
+                outputChannel = ref Unsafe.Add(ref outputChannel, 1);
+                
+                xStart = xEnd;
+                x0 = x1;
+            }
+            
+            outputTaskQueue = outputTaskQueue
+                .ContinueWith(_ => encoder.WriteData(outputBuffer, cancellationToken: cancellationToken), cancellationToken);
+            
+            yStart = yEnd;
+        }
+
+        await outputTaskQueue;
+        encoder.WriteEndOfFile(cancellationToken);
+    }
+    
+    private void MapRow(
+        int rowOffset,
+        int yOffset,
+        IBuffer<int> boundsMatrix,
+        int count,
+        IBuffer<Int32Pixel> destination,
+        bool appendMode = false)
+    {
+        var sourceMap = boundsMatrix.Span[..count];
+        var currentTile = TileManager.GetAdjacent(TileOrigin, 0, rowOffset);
+        var xAdder = Int32Pixel.Zero;
+        var xOffset = 0;
+        var written = 0;
+        var destinationSpan = destination.Span;
+        var readBufferSpan = _mmfReadBuffer.Span;
+        while (true)
+        {
+            currentTile.Integral.Acquire(yOffset, readBufferSpan);
+            int localX;
+            if (appendMode)
+            {
+                while (written < sourceMap.Length && (localX = sourceMap[written] - xOffset) < TileWidth)
+                {
+                    destinationSpan[written] += readBufferSpan[localX];
+                    destinationSpan[written] += xAdder;
+                    written++;
+                }
+            }
+            else
+            {
+                while (written < sourceMap.Length && (localX = sourceMap[written] - xOffset) < TileWidth)
+                {
+                    destinationSpan[written] = readBufferSpan[localX];
+                    destinationSpan[written] += xAdder;
+                    written++;
+                }
+            }
+
+            if (written >= sourceMap.Length)
+                break;
+
+            xAdder += readBufferSpan[RightmostPixelIndex];
+            xOffset += TileWidth;
+            currentTile = TileManager.GetAdjacent(currentTile, 1, 0);
+        }
+    }
+
+    public void Dispose()
+    {
+        _mmfReadBuffer.Dispose();
+        GC.SuppressFinalize(this);
+    }
+}

Domain/StitchATon2.Domain.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFramework>net8.0</TargetFramework>
+        <TargetFramework>net9.0</TargetFramework>
         <ImplicitUsings>enable</ImplicitUsings>
         <Nullable>enable</Nullable>
     </PropertyGroup>

Domain/Utils.cs

@@ -20,6 +20,7 @@ public static class Utils
         return (a + b - 1) / b;
     }
     
+    [Pure]
     public static (int Column, int Row) GetSBSCoordinate(string coordinate)
     {
         var column = coordinate[^1] - '0';
@@ -33,7 +34,13 @@ public static class Utils
         return (column, row);
     }
     
-    
+    /// <summary>
+    /// Performs a SIMD-accelerated calculation that generates a buffer of bounded, scaled indices.
+    /// </summary>
+    /// <param name="scaleFactor">The amount by which to scale the sequence values.</param>
+    /// <param name="length">The total number of scalar values to generate.</param>
+    /// <param name="max">Upper limit (exclusive) for clamping values.</param>
+    /// <param name="offset">The offset to apply before clamping.</param>
     public static IBuffer<int> BoundsMatrix(float scaleFactor, int length, int max, int offset)
     {
         var vectorSize = DivCeil(length, Vector<float>.Count);
@@ -45,14 +52,13 @@ public static class Utils
         var vectorMax = new Vector<int>(max - 1);
         var vectorScale = new Vector<float>(scaleFactor);
 
-        var vectorSequence = SequenceVector(0f, 1f);
+        var vectorSequence = Vector.CreateSequence(0f, 1f);
 
         var seq = 0f;
         for (var i = 0; i < vectorSize; i++, seq += Vector<float>.Count)
         {
             var sequence = new Vector<float>(seq) + vectorSequence;
-            span[i] = Vector.Multiply(sequence, vectorScale);
-            span[i] = Vector.Add(span[i], vectorScale);
+            span[i] = Vector.FusedMultiplyAdd(sequence, vectorScale, vectorScale);
             span[i] = Vector.Ceiling(span[i]);
         }
         
@@ -62,23 +68,9 @@ public static class Utils
         {
             resultSpan[i] = Vector.ConvertToInt32(span[i]);
             resultSpan[i] = Vector.Add(resultSpan[i], vectorOffset);
-            resultSpan[i] = Vector.Min(resultSpan[i], vectorMax);
-            resultSpan[i] = Vector.Max(resultSpan[i], vectorMin);
+            resultSpan[i] = Vector.ClampNative(resultSpan[i], vectorMin, vectorMax);
         }
 
         return result;
     }
-
-    private static Vector<float> SequenceVector(float start, float step)
-    {
-        var vector = Vector<float>.Zero;
-        ref var reference = ref Unsafe.As<Vector<float>, float>(ref vector);
-        for (var i = 0; i < Vector<float>.Count; i++)
-        {
-            ref var current = ref Unsafe.Add(ref reference, i);
-            current = start + step * i;
-        }
-
-        return vector;
-    }
 }

Infra/Buffers/ImmovableMemory.cs

@@ -0,0 +1,37 @@
+using System.Buffers;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+namespace StitchATon2.Infra.Buffers;
+
+internal sealed unsafe class ImmovableMemory<T> : MemoryManager<T> where T : unmanaged
+{
+    private readonly T* _pointer;
+    private readonly int _length;
+    private bool _disposed;
+
+    public ImmovableMemory(int count)
+    {
+        _pointer = (T*)NativeMemory.Alloc((nuint)count, (nuint)Unsafe.SizeOf<T>());
+        _length = count;
+    }
+    
+    protected override void Dispose(bool disposing)
+    {
+        if (!_disposed)
+        {
+            NativeMemory.Free(_pointer);
+            _disposed = true;
+        }
+    }
+
+    public override Span<T> GetSpan()
+        => new(_pointer, _length);
+
+    public override MemoryHandle Pin(int elementIndex = 0)
+        => new(_pointer + elementIndex);
+
+    public override void Unpin()
+    {
+    }
+}

Infra/Buffers/MemoryAllocator.cs

@@ -12,4 +12,7 @@ public static class MemoryAllocator
     
     public static ArrayOwner<T> AllocateArray<T>(int count) where T : unmanaged
         => new(ArrayPool<T>.Shared, count);
+
+    public static MemoryManager<T> AllocateImmovable<T>(int count) where T : unmanaged
+        => new ImmovableMemory<T>(count);
 }

Infra/Buffers/UnmanagedMemory.cs

@@ -3,18 +3,23 @@ using System.Runtime.InteropServices;
 
 namespace StitchATon2.Infra.Buffers;
 
+/// <summary>
+/// Provide non-thread safe anti GC contiguous memory. 
+/// </summary>
+/// <typeparam name="T"></typeparam>
 internal sealed unsafe class UnmanagedMemory<T> : IBuffer<T> where T : unmanaged
 {
-    private readonly void* _pointer;
+    private readonly T* _pointer;
     private readonly int _count;
+    private bool _disposed;
 
-    public ref T this[int index] => ref Unsafe.AsRef<T>((T*)_pointer + index); // *((T*)_pointer + index);
+    public ref T this[int index] => ref Unsafe.AsRef<T>(_pointer + index);
 
     public Span<T> Span => new(_pointer, _count);
 
     public UnmanagedMemory(int count)
     {
-        _pointer = NativeMemory.Alloc((nuint)count, (nuint)Unsafe.SizeOf<T>());
+        _pointer = (T*)NativeMemory.Alloc((nuint)count, (nuint)Unsafe.SizeOf<T>());
         _count = count;
     }
     
@@ -22,7 +27,11 @@ internal sealed unsafe class UnmanagedMemory<T> : IBuffer<T> where T : unmanaged
 
     public void Dispose()
     {
-        NativeMemory.Free(_pointer);
-        GC.SuppressFinalize(this);
+        if (!_disposed)
+        {
+            NativeMemory.Free(_pointer);
+            GC.SuppressFinalize(this);
+            _disposed = true;
+        }
     }
 }

Infra/Encoders/PngPipeEncoder.cs

@@ -0,0 +1,135 @@
+using System.Buffers;
+using System.Buffers.Binary;
+using System.IO.Compression;
+using System.IO.Pipelines;
+using StitchATon2.Infra.Buffers;
+
+namespace StitchATon2.Infra.Encoders;
+
+public class PngPipeEncoder : IDisposable
+{
+    private const int BufferSize = 8 * 1024;
+    private const int FlushThreshold = 1024;
+    
+    private readonly PipeWriter _outputPipe;
+    private readonly MemoryStream _memoryStream;
+    private readonly int _width;
+    private readonly int _height;
+
+    private readonly ZLibStream _zlibStream;
+    private bool _disposed;
+    private bool _shouldFlush;
+    
+    public PngPipeEncoder(PipeWriter outputPipe, int width, int height)
+    {
+        _outputPipe = outputPipe;
+        _width = width;
+        _height = height;
+        _memoryStream = new MemoryStream(BufferSize * 2);
+        _zlibStream = new ZLibStream(_memoryStream, CompressionLevel.Optimal, leaveOpen: true);
+        _memoryStream.SetLength(8);
+        _memoryStream.Position = 8;
+    }
+
+    ~PngPipeEncoder() => Dispose();
+
+    public void WriteHeader()
+    {
+        Span<byte> headerBytes = [
+            0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A, // PNG Signature
+            0x00, 0x00, 0x00, 0x0D, // Length
+            
+            // IHDR chunk
+            0x49, 0x48, 0x44, 0x52, // IHDR
+            0x00, 0x00, 0x00, 0x00, // Reserve to write Width
+            0x00, 0x00, 0x00, 0x00, // Reserve to write Height
+            0x08, // Bit depth
+            0x02, // Color type
+            0x00, // Compression method
+            0x00, // Filter method
+            0x00, // Interlace method
+            0x00, 0x00, 0x00, 0x00, // Reserve to write CRC-32
+        ];
+        
+        BinaryPrimitives.WriteInt32BigEndian(headerBytes[16..], _width);
+        BinaryPrimitives.WriteInt32BigEndian(headerBytes[20..], _height);
+        var crc = Crc32.Compute(headerBytes.Slice(12, 17));
+        
+        BinaryPrimitives.WriteUInt32BigEndian(headerBytes[29..], crc);
+        
+        _outputPipe.Write(headerBytes);
+    }
+
+    public void WriteData(IBuffer<byte> buffer, bool disposeBuffer = true, CancellationToken cancellationToken = default)
+    {
+        _zlibStream.Write([0]);
+        
+        var dataSlice = buffer.Span;
+        while (dataSlice.Length > FlushThreshold)
+        {
+            _zlibStream.Write(dataSlice[..FlushThreshold]);
+            _zlibStream.Flush();
+            dataSlice = dataSlice[FlushThreshold..];
+            if(_memoryStream.Length >= BufferSize)
+                Flush(cancellationToken);
+        }
+        
+        if (dataSlice.Length > 0)
+        {
+            _zlibStream.Write(dataSlice);
+            _zlibStream.Flush();
+            _shouldFlush = true;
+        }
+        
+        if(disposeBuffer) buffer.Dispose();
+    }
+
+    private void Flush(CancellationToken cancellationToken)
+    {
+        _zlibStream.Flush();
+        var dataSize = (int)(_memoryStream.Length - 8);
+
+        _memoryStream.Write("\0\0\0\0"u8);
+
+        _memoryStream.Position = 4;
+        _memoryStream.Write("IDAT"u8);
+
+        var buffer = _memoryStream.GetBuffer();
+        BinaryPrimitives.WriteInt32BigEndian(buffer, dataSize);
+
+        // write Crc
+        var crc = Crc32.Compute(buffer.AsSpan(4, dataSize + 4));
+        BinaryPrimitives.WriteUInt32BigEndian(buffer.AsSpan(dataSize + 8), crc);
+            
+        _outputPipe.Write(buffer.AsSpan(0, dataSize + 12));
+        _memoryStream.SetLength(8);
+        _memoryStream.Position = 8;
+        _shouldFlush = false;
+    }
+
+    public void WriteEndOfFile(CancellationToken cancellationToken = default)
+    {
+        if(_shouldFlush)
+            Flush(cancellationToken);
+        
+        Span<byte> endChunk = [
+            0x00, 0x00, 0x00, 0x00, // Length
+            0x49, 0x45, 0x4E, 0x44, // IEND
+            0xAE, 0x42, 0x60, 0x82, // Crc
+        ];
+        
+        _outputPipe.Write(endChunk);
+        Dispose();
+    }
+
+    public void Dispose()
+    {
+        if (!_disposed)
+        {
+            _zlibStream.Dispose();
+            _memoryStream.Dispose();
+            _disposed = true;
+            GC.SuppressFinalize(this);
+        }
+    }
+}

Infra/ImageIntegral.cs

@@ -20,7 +20,7 @@ public class ImageIntegral : IDisposable
 
     private IMemoryOwner<ManualResetEventSlim>? _rowLocks;
     private MemoryMappedFile? _memoryMappedFile;
-    private readonly object _lock = new();
+    private readonly Lock _lock = new();
 
     private readonly ManualResetEventSlim _queueLock = new(true);
     private readonly ManualResetEventSlim _initializationLock = new(false);
@@ -249,7 +249,7 @@ public class ImageIntegral : IDisposable
         view.DangerousReadSpan(0, buffer, 0, _width);
     }
 
-    private void ReadRow(int row, IBuffer<Int32Pixel> buffer)
+    private void ReadRow(int row, ArrayOwner<Int32Pixel> buffer)
     {
         using var view = AcquireView(row, MemoryMappedFileAccess.Read);
         view.DangerousReadSpan(0, buffer.Span, 0, _width);

Infra/StitchATon2.Infra.csproj

@@ -1,14 +1,14 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFramework>net8.0</TargetFramework>
+        <TargetFramework>net9.0</TargetFramework>
         <ImplicitUsings>enable</ImplicitUsings>
         <Nullable>enable</Nullable>
         <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     </PropertyGroup>
 
     <ItemGroup>
-      <PackageReference Include="SixLabors.ImageSharp" Version="3.1.10" />
+      <PackageReference Include="SixLabors.ImageSharp" Version="3.1.11" />
     </ItemGroup>
 
 </Project>

Infra/Synchronization/TaskHelper.cs

@@ -2,11 +2,7 @@ namespace StitchATon2.Infra.Synchronization;
 
 public static class TaskHelper
 {
-    public static TaskFactory CreateTaskFactory()
-    {
-        return new TaskFactory(
-            TaskCreationOptions.AttachedToParent,
-            TaskContinuationOptions.ExecuteSynchronously
-            );
-    }
+    public static readonly TaskFactory SynchronizedTaskFactory = new(
+        TaskCreationOptions.LongRunning,
+        TaskContinuationOptions.ExecuteSynchronously);
 }

Infra/Utils.cs

@@ -7,19 +7,13 @@ namespace StitchATon2.Infra;
 
 public static class Utils
 {
-    [UnsafeAccessor(UnsafeAccessorKind.Field, Name = "_buffer")]
-    private static extern ref SafeBuffer GetSafeBuffer(this UnmanagedMemoryAccessor view);
-
-    [UnsafeAccessor(UnsafeAccessorKind.Field, Name = "_offset")]
-    private static extern ref long GetOffset(this UnmanagedMemoryAccessor view);
-
     private static unsafe uint AlignedSizeOf<T>() where T : unmanaged
     {
         uint size = (uint)sizeof(T);
         return size is 1 or 2 ? size : (uint)((size + 3) & (~3));
     }
 
-    public static void DangerousReadSpan<T>(this UnmanagedMemoryAccessor view, long position, Span<T> span, int offset, int count)
+    internal static void DangerousReadSpan<T>(this MemoryMappedViewAccessor view, long position, Span<T> span, int offset, int count)
         where T : unmanaged
     {
         uint sizeOfT = AlignedSizeOf<T>();
@@ -38,8 +32,8 @@ public static class Utils
             }
         }
 
-        var byteOffset = (ulong)(view.GetOffset() + position);
-        view.GetSafeBuffer().ReadSpan(byteOffset, span.Slice(offset, n));
+        var byteOffset = (ulong)(view.PointerOffset + position);
+        view.SafeMemoryMappedViewHandle.ReadSpan(byteOffset, span.Slice(offset, n));
     }
 
     public static ArrayOwner<T> Clone<T>(this ArrayOwner<T> arrayOwner, int length) where T : unmanaged
@@ -48,9 +42,4 @@ public static class Utils
         Array.Copy(arrayOwner.Array, 0, newArrayOwner.Array, 0, length);
         return newArrayOwner;
     }
-
-    public static void CopyTo<T>(this ArrayOwner<T> arrayOwner, ArrayOwner<T> target, int length) where T : unmanaged
-    {
-        Array.Copy(arrayOwner.Array, 0, target.Array, 0, length);
-    }
 }

global.json

@@ -1,6 +1,6 @@
 {
   "sdk": {
-    "version": "8.0.0",
+    "version": "9.0.0",
     "rollForward": "latestMinor",
     "allowPrerelease": false
   }