Why I stopped fighting with libgdiplus and built my own invoice API (with native PIX support)

Andrea Lima — Sat, 04 Apr 2026 14:02:24 +0000

you've ever deployed a PDF-generating app to a Linux Docker container, you know this feeling:

System.Drawing.Common is not supported on this platform

Fonts turning into squares. Alpine images bloating to 800MB. Hours lost on libgdiplus configs that work locally and break in CI/CD.
I got tired of it. So I built SwiftInvoice — a stateless API that turns JSON into print-ready PDFs. You POST the data, you get a binary PDF stream back. No local dependencies. No font hell.

Here's what it generates:

Three languages, three currencies, native PIX QR Code generation — all from the same endpoint.

Before vs. After

Before:

dockerfile

FROM mcr.microsoft.com/dotnet/aspnet:8.0
RUN apt-get update && apt-get install -y \
    libgdiplus libx11-6 fontconfig \
    && ln -s /usr/lib/libgdiplus.so /usr/lib/gdiplus.dll

After:

dockerfile

FROM mcr.microsoft.com/dotnet/aspnet:8.0-alpine
# That's it. SwiftInvoice handles the rest.

Quick start (Node.js):

javascript
const response = await axios.request({
    method: 'POST',
    url: 'https://swiftinvoice.p.rapidapi.com/GenerateInvoice',
    headers: {
        'X-RapidAPI-Key': 'YOUR_KEY',
        'X-RapidAPI-Host': 'swiftinvoice.p.rapidapi.com'
    },
    data: {
        InvoiceNumber: "2026-001",
        Language: "pt-BR",
        Currency: "BRL",
        PixKey: "your-pix-key@email.com", // Generates QR Code automatically
        Items: [
            { Description: "API Development", Quantity: 1, UnitPrice: 4500.00 }
        ]
    },
    responseType: 'arraybuffer'
});

Full examples in C#, Python, PHP and Go available in the repository.
Free tier available — no credit card required. If you're tired of PDF dependency hell, give it a try.

👉 SwiftInvoice on RapidAPI

How are you handling PDF generation in your stack? Still using local libraries?

Stop Fighting PDF Generation: How I Built a Stateless API for Global Invoices

Andrea Lima — Wed, 25 Mar 2026 14:31:49 +0000

Generating professional PDFs in the backend is a notorious headache. If you've ever dealt with:

❌ Broken layouts when moving from Dev to Docker/Linux.

❌ Missing fonts or "libgdiplus" issues on the server.

❌ Complexity in localizing currencies, dates, and taxes.

❌ Generating QR Codes (like PIX) dynamically inside the document.

...then you know the struggle.

The Solution: A Stateless Approach
I decided to build SwiftInvoice, a high-performance API designed to handle the "boring parts" of billing. Instead of installing heavy engines on your main server, you just send a JSON and get a print-ready PDF stream back.

Why this matters for your architecture:
Serverless Ready: Since it's stateless, you don't store anything. Perfect for clean, scalable microservices.

Native Localization: It handles English, Portuguese, and Spanish formatting (culture-aware) automatically.

High Performance: Built on .NET/Azure, it maintains a 100% service level for critical billing tasks.

Quick Example (Node.js/Axios):

JavaScript
const response = await axios.post('https://swiftinvoice.p.rapidapi.com/GenerateInvoice', {
    InvoiceNumber: "2026-001",
    SenderName: "Your Startup",
    PixKey: "your-pix-key", // Native PIX support!
    Items: [{ Description: "API Subscription", Quantity: 1, UnitPrice: 25.00 }]
}, { responseType: 'arraybuffer', headers: { 'X-RapidAPI-Key': 'YOUR_KEY' } });

Try it out
I've just released it on RapidAPI with a Free Basic Tier for the community to test and integrate into their side projects.

👉 Check the Playground: swiftinvoice

I’d love to hear your feedback: What’s your biggest pain point when generating reports or invoices today?

DEV Community: Andrea Lima

Why I stopped fighting with libgdiplus and built my own invoice API (with native PIX support)

Stop Fighting PDF Generation: How I Built a Stateless API for Global Invoices