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Overview

PDF4LLM can extract images and graphics from documents in two ways: writing them as files to disk, or embedding them as Base64-encoded data URIs directly in the Markdown output. When images are written to disk, their paths are referenced inline using standard Markdown image syntax. Image extraction is disabled by default. To enable it, pass writeImages: true to ToMarkdown(). 
using PDF4LLM;

string mdText = PdfExtractor.ToMarkdown("document.pdf", writeImages: true);

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Writing images to disk

When writeImages: true is set, each image found in the document is saved as an individual file. The path to each image is embedded in the Markdown output: 
![image](assets/images/document.pdf-0-1.png)
By default, images are written to the process working directory. Use imagePath to specify a different output directory: 
string mdText = PdfExtractor.ToMarkdown(
    "document.pdf",
    writeImages: true,
    imagePath:   "assets/images/"
);
Unlike the Python library, PDF4LLM for .NET does not create the output directory automatically. Create it before calling ToMarkdown() or you will get a DirectoryNotFoundException:
Directory.CreateDirectory("assets/images/");

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Image format

Use the imageFormat parameter to control the file format of extracted images. Pass the format as a lowercase file extension string: 
string mdText = PdfExtractor.ToMarkdown(
    "document.pdf",
    writeImages:  true,
    imagePath:    "assets/images/",
    imageFormat:  "jpg"
);
FormatBest forNotes
"png"Diagrams, screenshots, chartsLossless. Larger file size. Default.
"jpg"Photographs, scanned pagesLossy. Smaller file size.
"webp"Web deliveryGood compression, broad browser support.
"tiff"Archival, OCR pre-processingLossless. Large file size.
"bmp"Maximum compatibilityUncompressed. Very large file size.
"pnm"OCR pre-processing pipelinesPortable bitmap format.
Use "png" when image fidelity matters — for example, when extracting charts, diagrams, or figures that contain readable text. Use "jpg" for photographic content where file size is a concern.

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Embedded vs. file images

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File images (write to disk)

When using ToMarkdown() with writeImages: true, images are saved to disk and referenced by path in the Markdown output: 
string mdText = PdfExtractor.ToMarkdown(
    "document.pdf",
    writeImages:  true,
    imagePath:    "assets/",
    imageFormat:  "png"
);
The Markdown output will contain image references like: 
Some preceding text.

![image](assets/document.pdf-0-1.png)

Some following text.

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Embedded images (inline Base64)

Set embedImages: true to encode images as Base64 data URIs and embed them directly in the Markdown — no files are written to disk: 
string mdText = PdfExtractor.ToMarkdown("document.pdf", embedImages: true);
The Markdown output will contain inline data URIs: 
Some preceding text.

![image](data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAA...)

Some following text.
This produces a fully self-contained output string with no external file dependencies — useful when passing Markdown directly to an LLM or storing it in a vector store.
writeImages and embedImages are mutually exclusive. If both are set to true, embedImages takes precedence and no files are written to disk.

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Vector graphics

PDF4LLM detects vector drawings — lines, shapes, and filled regions — and includes their bounding boxes in the layout analysis. Vector graphic regions are represented as "image" type blocks in ToJson() output, giving you their position on the page so you can identify and handle them in your pipeline.

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Image file naming

Extracted image files are named automatically using the pattern: 
{imagePath}/{sourceFilename}-{pageNumber}-{imageIndex}.{imageFormat}
For example, the second image on page 3 of document.pdf, saved as PNG to assets/images/: 
assets/images/document.pdf-2-2.png
Page numbers are zero-based. Image indices are one-based and reset on each new page.

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Full example

using System.IO;
using PDF4LLM;

string imagePath = "output/images/";
Directory.CreateDirectory(imagePath);

// Extract Markdown with images saved to disk
string mdText = PdfExtractor.ToMarkdown(
    "report.pdf",
    writeImages:  true,
    imagePath:    imagePath,
    imageFormat:  "png"
);

// Save the Markdown file
File.WriteAllText("output/report.md", mdText, System.Text.Encoding.UTF8);

Console.WriteLine("Done.");
Console.WriteLine($"Images saved to: {imagePath}");
Console.WriteLine("Markdown saved to: output/report.md");
For the full API signature, see the ToMarkdown() API reference.

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Next steps

Extract Markdown

Full walkthrough of ToMarkdown() with all common options.

Extract JSON

Access image bounding boxes via the JSON output.

Tables

Table extraction explained.