Self-Contained PDF Generation for Cloud and Serverless Apps

The Business Problem

An invoicing service moves to Azure or AWS Lambda, where file-system access is limited and ephemeral, so the image paths that worked locally no longer resolve. A reporting tool emails documents that must still display correctly years later, long after the original asset server has changed. A pipeline assembles documents from images generated at runtime that were never saved to disk. In each case, external image references are a liability.

Embedding Images as Data URIs

The pattern is three steps: read the image bytes, convert them to base64, and place the result in an <img> tag with the matching MIME type. The rendered PDF then holds the image inside the file.

using IronPdf;
using System;

byte[] imageBytes = System.IO.File.ReadAllBytes("logo.png");
string dataUri = "data:image/png;base64," + Convert.ToBase64String(imageBytes);
string html = $"<img src='{dataUri}'>";

var renderer = new ChromePdfRenderer();
var pdf = renderer.RenderHtmlAsPdf(html);
pdf.SaveAs("self-contained.pdf");

using IronPdf;
using System;

byte[] imageBytes = System.IO.File.ReadAllBytes("logo.png");
string dataUri = "data:image/png;base64," + Convert.ToBase64String(imageBytes);
string html = $"<img src='{dataUri}'>";

var renderer = new ChromePdfRenderer();
var pdf = renderer.RenderHtmlAsPdf(html);
pdf.SaveAs("self-contained.pdf");

Imports IronPdf
Imports System

Dim imageBytes As Byte() = System.IO.File.ReadAllBytes("logo.png")
Dim dataUri As String = "data:image/png;base64," & Convert.ToBase64String(imageBytes)
Dim html As String = $"<img src='{dataUri}'>"

Dim renderer As New ChromePdfRenderer()
Dim pdf = renderer.RenderHtmlAsPdf(html)
pdf.SaveAs("self-contained.pdf")

The same approach works for runtime-generated images, such as a chart or barcode produced in memory, by encoding the bytes directly without writing a temporary file. Multiple formats are supported as long as the data URI declares the right type: PNG, JPEG, GIF, SVG (image/svg+xml), and WebP.

Points to Plan For

• Base64 adds size: Encoding increases each image's byte size by roughly a third, which lands in both the HTML and the PDF. For image-heavy documents, compress or resize before encoding and apply PDF compression afterward.
• Match the MIME type: The prefix must match the format, such as data:image/jpeg;base64, for a JPEG, or the image will not render.
• No file-system dependency: Because the image travels inside the document, the render does not rely on a reachable path or asset server, which is what makes it dependable in cloud and container deployments.
• Fewer fetches: Inline images avoid extra HTTP or file-system calls during rendering, which helps throughput when a document contains many small images.

Result

By embedding images as data URIs, teams generate PDFs that render identically whether they run on a laptop or in a serverless function, and that keep every image intact when emailed or archived. Full format details and examples are in the embed images with DataURIs guide.