Respect PreferContiguousImageBuffers in decoders

src/ImageSharp/Formats/Jpeg/Components/Decoder/SpectralConverter{TPixel}.cs

@@ -111,7 +111,10 @@ public override void InjectFrameData(JpegFrame frame, IRawJpegData jpegData)
             this.pixelRowsPerStep = majorVerticalSamplingFactor * blockPixelHeight;
 
             // pixel buffer for resulting image
-            this.pixelBuffer = allocator.Allocate2D<TPixel>(frame.PixelWidth, frame.PixelHeight);
+            this.pixelBuffer = allocator.Allocate2D<TPixel>(
+                frame.PixelWidth,
+                frame.PixelHeight,
+                this.configuration.PreferContiguousImageBuffers);
             this.paddedProxyPixelRow = allocator.Allocate<TPixel>(frame.PixelWidth + 3);
 
             // component processors from spectral to Rgba32

src/ImageSharp/Image.Decode.cs

@@ -37,8 +37,10 @@ internal static Image<TPixel> CreateUninitialized<TPixel>(
             ImageMetadata metadata)
             where TPixel : unmanaged, IPixel<TPixel>
         {
-            Buffer2D<TPixel> uninitializedMemoryBuffer =
-                configuration.MemoryAllocator.Allocate2D<TPixel>(width, height);
+            Buffer2D<TPixel> uninitializedMemoryBuffer = configuration.MemoryAllocator.Allocate2D<TPixel>(
+                    width,
+                    height,
+                    configuration.PreferContiguousImageBuffers);
             return new Image<TPixel>(configuration, uninitializedMemoryBuffer.FastMemoryGroup, width, height, metadata);
         }
 

tests/ImageSharp.Tests/Image/LargeImageIntegrationTests.cs

@@ -2,7 +2,10 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System;
+using System.IO;
 using Microsoft.DotNet.RemoteExecutor;
+using SixLabors.ImageSharp.Advanced;
+using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Processing;
@@ -32,9 +35,40 @@ static void RunTest()
                 Configuration configuration = Configuration.Default.Clone();
                 configuration.PreferContiguousImageBuffers = true;
 
-                using var image = new Image<Rgba32>(configuration, 8192, 4096);
+                using var image = new Image<Rgba32>(configuration, 2048, 2048);
                 Assert.True(image.DangerousTryGetSinglePixelMemory(out Memory<Rgba32> mem));
-                Assert.Equal(8192 * 4096, mem.Length);
+                Assert.Equal(2048 * 2048, mem.Length);
+            }
+        }
+
+        [Theory]
+        [InlineData("bmp")]
+        [InlineData("png")]
+        [InlineData("jpeg")]
+        [InlineData("gif")]
+        [InlineData("tiff")]
+        [InlineData("webp")]
+        public void PreferContiguousImageBuffers_LoadImage_BufferIsContiguous(string formatOuter)
+        {
+            // Run remotely to avoid large allocation in the test process:
+            RemoteExecutor.Invoke(RunTest, formatOuter).Dispose();
+
+            static void RunTest(string formatInner)
+            {
+                Configuration configuration = Configuration.Default.Clone();
+                configuration.PreferContiguousImageBuffers = true;
+                IImageEncoder encoder = configuration.ImageFormatsManager.FindEncoder(
+                    configuration.ImageFormatsManager.FindFormatByFileExtension(formatInner));
+                string dir = TestEnvironment.CreateOutputDirectory(".Temp");
+                string path = Path.Combine(dir, $"{Guid.NewGuid().ToString()}.{formatInner}");
+                using (Image<Rgba32> temp = new(2048, 2048))
+                {
+                    temp.Save(path, encoder);
+                }
+
+                using var image = Image.Load<Rgba32>(configuration, path);
+                File.Delete(path);
+                Assert.Equal(1, image.GetPixelMemoryGroup().Count);
             }
         }