MagicScaler with SkiaSharp on Linux

Program.cs

using System;
using System.IO;
using System.Drawing;
using System.Runtime.InteropServices;

using SkiaSharp;
using PhotoSauce.MagicScaler;

class Program
{
    // Ideally an IPixelSource implementation would use Skia's ScanLine or Incremental decoding
    // if supported by the codec.  This one wraps a fully-decoded image.
    private class SkiaPixelSource : BitmapPixelSource
    {
        private readonly byte[] pixels;

        public SkiaPixelSource(Guid format, int width, int height, int stride, byte[] pixels)
            : base(format, width, height, stride) => this.pixels = pixels;

        protected override ReadOnlySpan<byte> Span => pixels.AsSpan();
    }

    public static void Main()
    {
        string inImgPath = "/mnt/c/img/bigimage.jpg";
        string outImgPath = "/mnt/c/img/smallimage.jpg";

        // Use SKCodec so we can control the details of the decoding.
        using var skCodec = SKCodec.Create(inImgPath);
        var skSrcInfo = skCodec.Info;

        // Alternate SKImageInfo settings force the decoder to convert the pixel format on decode.
        // This could be smarter about pixel format mapping. For now, we pick a format that is compatible between
        // Skia and MagicScaler (SkiaSharp.SKColorType.Bgra8888 == PhotoSauce.MagicScaler.PixelFormats.Bgra32bpp)
        // Since we can't retrieve an ICC profile directly from Skia, we ask it to convert to sRGB on decode.
        // Note that this sample doesn't handle Exif Orientation, which is encoded in `SKCodec.EncodedOrigin`
        var skDecodeInfo = new SKImageInfo {
            Width = skSrcInfo.Width,
            Height = skSrcInfo.Height,
            ColorType = SKColorType.Bgra8888,
            AlphaType = SKAlphaType.Unpremul,
            ColorSpace = SKColorSpace.CreateSrgb()
        };

        // Create a buffer to hold the decoded pixels.
        int inStride = skDecodeInfo.Width * skDecodeInfo.BytesPerPixel;
        var inPixels = new byte[inStride * skDecodeInfo.Height];
        var inHandle = GCHandle.Alloc(inPixels, GCHandleType.Pinned);

        // Decode the input image into the buffer.
        skCodec.GetPixels(skDecodeInfo, inHandle.AddrOfPinnedObject(), inStride, SKCodecOptions.Default);
        inHandle.Free();

        // Create an IPixelSource to wrap the buffer.  The pixel format must be binary-compatible with the Skia pixel format.
        using var psSource = new SkiaPixelSource(PixelFormats.Bgra32bpp, skDecodeInfo.Width, skDecodeInfo.Height, inStride, inPixels);

        // Create a MagicScaler pipeline to resize the image, then retrieve its IPixelSource.
        using var psPipeline = MagicImageProcessor.BuildPipeline(psSource, new ProcessImageSettings { Width = 400 });
        var psOutput = psPipeline.PixelSource;

        // Retrieve the target size from the pipeline.  We keep the pixel format and color space from the source.
        var skDstInfo = skDecodeInfo.WithSize(psOutput.Width, psOutput.Height);

        // Create a buffer for the resized image.
        int outStride = skDstInfo.Width * skDstInfo.BytesPerPixel;
        var outPixels = new byte[outStride * skDstInfo.Height];
        var outHandle = GCHandle.Alloc(outPixels, GCHandleType.Pinned);

        // Resize the image into the buffer.
        psOutput.CopyPixels(new Rectangle(0, 0, psOutput.Width, psOutput.Height), outStride, outPixels);

        // Wrap the buffer in an SKImage.
        using var skDstImage = SKImage.FromPixels(skDstInfo, outHandle.AddrOfPinnedObject(), outStride);

        // And save the encoded output.
        using var outFile = new FileStream(outImgPath, FileMode.Create);
        skDstImage.Encode(SKEncodedImageFormat.Jpeg, psPipeline.Settings.JpegQuality).SaveTo(outFile);
        outHandle.Free();
    }
}

SkiaPlusMagicScaler.csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp3.1</TargetFramework>
    <RestoreAdditionalProjectSources>https://pkgs.dev.azure.com/saucecontrol/PhotoSauce/_packaging/photosauce_ci/nuget/v3/index.json</RestoreAdditionalProjectSources>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="PhotoSauce.MagicScaler" Version="0.10.4-ci*" />
    <PackageReference Include="SkiaSharp" Version="1.68.1.1" />
    <PackageReference Condition="$([MSBuild]::IsOSPlatform('linux'))" Include="SkiaSharp.NativeAssets.Linux" Version="1.68.1.1" />
  </ItemGroup>

</Project>