SlimLO 0.1.4

SlimLO

Managed .NET library for high-fidelity DOCX-to-PDF conversion.

SlimLO provides a thread-safe, async API backed by a minimal, purpose-built LibreOffice engine. Each conversion runs in an isolated native worker process — if LibreOffice crashes on a malformed document, only the worker is killed; your .NET process is never affected.

Features

• Process isolation — crash-resilient, no shared state between conversions
• Thread-safe — MaxWorkers > 1 enables true parallel conversion across separate OS processes
• Multiple conversion modes — file-path (zero-copy), byte buffer (zero disk I/O), and stream-to-stream
• Font diagnostics — font substitution warnings surfaced as structured ConversionDiagnostic objects
• PDF options — PDF/A (1a, 2a, 3a), tagged PDF, JPEG quality, DPI, page ranges
• Cross-platform — Linux x64/arm64, macOS arm64/x64, Windows x64/ARM64
• Wide .NET support — targets netstandard2.0 (.NET Framework 4.6.1+) and net8.0

Installation

Install the managed SDK and the native assets package for your target platform:

<PackageReference Include="SlimLO" Version="0.1.0" />


<PackageReference Include="SlimLO.NativeAssets.Linux" Version="0.1.0"
    Condition="$([MSBuild]::IsOSPlatform('Linux'))" />
<PackageReference Include="SlimLO.NativeAssets.macOS" Version="0.1.0"
    Condition="$([MSBuild]::IsOSPlatform('OSX'))" />
<PackageReference Include="SlimLO.NativeAssets.Windows" Version="0.1.0"
    Condition="$([MSBuild]::IsOSPlatform('Windows'))" />

Quick Start

using SlimLO;

await using var converter = PdfConverter.Create();

var result = await converter.ConvertAsync("input.docx", "output.pdf");
result.ThrowIfFailed();

Advanced Usage

await using var converter = PdfConverter.Create(new PdfConverterOptions
{
    FontDirectories = new[] { "/app/fonts" },
    MaxWorkers = 2,
    MaxConversionsPerWorker = 100,
    ConversionTimeout = TimeSpan.FromMinutes(5),
    WarmUp = true
});

// File to file
var result = await converter.ConvertAsync("input.docx", "output.pdf");

// Byte buffer (zero disk I/O)
byte[] docxBytes = await File.ReadAllBytesAsync("input.docx");
var bufResult = await converter.ConvertAsync(docxBytes.AsMemory(), DocumentFormat.Docx);
await File.WriteAllBytesAsync("output.pdf", bufResult.Data!);

// Stream to stream (ideal for ASP.NET)
var streamResult = await converter.ConvertAsync(
    Request.Body, Response.Body, DocumentFormat.Docx);

// PDF/A output with tagged PDF
var result2 = await converter.ConvertAsync("input.docx", "output.pdf",
    new ConversionOptions { PdfVersion = PdfVersion.PdfA2, TaggedPdf = true });

Platform Requirements

Architecture

Each conversion runs in a separate slimlo_worker native process that hosts a minimal LibreOffice engine (libmergedlo). The managed SDK communicates with workers via length-prefixed JSON over stdin/stdout pipes. A WorkerPool manages worker lifecycle, round-robin dispatch, and automatic crash recovery.

License

MPL-2.0. See GitHub repository for full details.