DocumentConverter

DocumentConverter is a powerful document converter library that supports HTML to PDF, XLSX, and DOCX conversion, as well as PDF, XLS, XLSX, DOC, and DOCX to HTML conversion. It provides a simple and efficient API for transforming documents between popular formats while preserving content and structure.

NuGet Version License: MIT

• 🔄 Bidirectional Conversion:
  • Document ➔ HTML: Convert legacy/modern Word, Excel, and PDF files into structured HTML.
  • HTML ➔ Document: Convert HTML content back into fully formatted .docx, .xlsx, or .pdf files.
• 🐧 100% Cross-Platform & Linux Ready: Completely decoupled from native OS dependencies like GDI+ or System.Drawing.Common for metadata lookup. Run it anywhere without Unix-compatibility workarounds.
• 🖼️ Advanced Image Processing:
  • Resolves Base64 Data URIs, local file paths, and remote HTTP/HTTPS image URLs (using a thread-safe, cancellation-supported downloader).
  • Preserves cell-relative image alignments in PDF and Excel (anchors images exactly inside their source table cells and auto-scales row heights to prevent overlapping content).
• ⚡ Performance & Memory Optimized:
  • Implements Registry Pattern for extensibility.
  • Cell Style Caching for NPOI Excel sheets to prevent Excel style limit exhaustion.
  • Efficient backtracking StringBuilder text-wrapping for PDF generation.

Install the package via NuGet:

dotnet add package DocumentConverter

Initialize the DocumentConverterService and perform conversions via file paths or streams:

using DocumentConverter;
using DocumentConverter.Models;
var service = new DocumentConverterService();
// Option A: Convert from a file path
Result<string> pathResult = service.ConvertToHtml("report.docx");
if (pathResult.IsSuccess)
{
 string html = pathResult.Value;
 File.WriteAllText("report.html", html);
}
// Option B: Convert from a stream (ideal for web uploads/downloads)
using (var stream = File.OpenRead("data.xlsx"))
{
 Result<string> streamResult = service.ConvertToHtml(stream, ".xlsx");
 if (streamResult.IsSuccess)
 {
 string htmlTable = streamResult.Value;
 }
}

You can convert HTML back to Word, Excel, or PDF documents. The library will write the file directly or return the raw bytes:

using DocumentConverter;
using DocumentConverter.Models;
var service = new DocumentConverterService();
string htmlContent = "<h1>Document Title</h1><p>This is a paragraph.</p>";
// Option A: Convert HTML and save directly to a file
Result<bool> fileResult = service.ConvertFromHtml(htmlContent, ".pdf", "output.pdf");
if (fileResult.IsSuccess)
{
 Console.WriteLine("PDF file generated successfully!");
}
// Option B: Convert HTML and retrieve the raw bytes
Result<byte[]> bytesResult = service.ConvertFromHtml(htmlContent, ".docx");
if (bytesResult.IsSuccess)
{
 byte[] docxBytes = bytesResult.Value;
 File.WriteAllBytes("output.docx", docxBytes);
}

Adding a new document format converter is simple. The service implements a Registry Pattern. You can register custom converters in DocumentConverterService by matching the IDocumentConverter (for Document ➔ HTML) and IHtmlToDocumentConverter (for HTML ➔ Document) interfaces.

This project is licensed under the MIT License.