Working with PDF documents is a common requirement in modern applications. Whether you are building a document management system , an ASP.NET web service , or a desktop viewer application , there are times when you need to display a PDF page as an image. Instead of embedding the full PDF viewer, you can convert PDF pages to JPG images and use them wherever images are supported.

In this guide, we will walk through a step-by-step tutorial on how to convert PDF files to JPG images using Spire.PDF for .NET. We’ll cover the basics of converting a single page, handling multiple pages, adjusting resolution and quality, saving images to streams, and even batch converting entire folders of PDFs.

By the end, you’ll have a clear understanding of how to implement PDF-to-image conversion in your .NET projects.

Table of Contents:

• Install .NET PDF-to-JPG Converter Library
• Core Method: SaveAsImage
• Steps to Convert PDF to JPG in C# .NET
• Convert a Single Page to JPG
• Convert Multiple Pages (All or Range)
• Advanced Conversion Options
  • Set Image Resolution/Quality
  • Save the Converted Images as Stream
  • Batch Conversion (Multiple PDFs)
• Troubleshooting & Best Practices
• Conclusion
• FAQs

Install .NET PDF-to-JPG Converter Library

To perform the conversion, we’ll use Spire.PDF for .NET , a library designed for developers who need full control over PDFs in C#. It supports reading, editing, and converting PDFs without requiring Adobe Acrobat or any third-party dependencies.

Installation via NuGet

You can install Spire.PDF directly into your project using NuGet Package Manager Console:

Install-Package Spire.PDF

Alternatively, open NuGet Package Manager in Visual Studio, search for Spire.PDF , and click Install.

Licensing Note

Spire.PDF offers a free version with limitations, allowing conversion of only the first few pages. For production use, a commercial license unlocks the full feature set.

Core Method: SaveAsImage

The heart of PDF-to-image conversion in Spire.PDF lies in the SaveAsImage() method provided by the PdfDocument class.

Here’s what you need to know:

• Syntax (overload 1):

• Image SaveAsImage(int pageIndex, PdfImageType imageType);

  • pageIndex: The zero-based index of the PDF page you want to convert.
  • imageType: The type of image to generate, typically PdfImageType.Bitmap.

• Syntax (overload 2 with resolution):

• Image SaveAsImage(int pageIndex, PdfImageType imageType, int dpiX, int dpiY);

  • dpiX, dpiY: Horizontal and vertical resolution (dots per inch).

  Higher DPI = better quality but larger file size.

Supported PdfImageType Values

• Bitmap → returns a raw image.
• Metafile → returns a vector image (less common for JPG export).

Most developers use Bitmap when exporting to JPG.

Steps to Convert PDF to JPG in C# .NET

1. Import the Spire.Pdf and System.Drawing namespaces.
2. Create a new PdfDocument instance.
3. Load the PDF file from the specified path.
4. Use SaveAsImage() to convert one or more pages into images.
5. Save the generated image(s) in JPG format.

Convert a Single Page to JPG

Here’s a simple workflow to convert a single PDF page to a JPG image:

using Spire.Pdf.Graphics;
using Spire.Pdf;
using System.Drawing.Imaging;
using System.Drawing;

namespace ConvertSpecificPageToPng
{
    class Program
    {
        static void Main(string[] args)
        {
            // Create a PdfDocument object
            PdfDocument doc = new PdfDocument();

            // Load a sample PDF document
            doc.LoadFromFile("C:\\Users\\Administrator\\Desktop\\sample.pdf");

            // Convert a specific page to a bitmap image
            Image image = doc.SaveAsImage(0, PdfImageType.Bitmap);

            // Save the image as a JPG file
            image.Save("ToJPG.jpg", ImageFormat.Jpeg);

            // Disposes resources
            doc.Dispose();
        }
    }
}

Output:

Spire.PDF supports converting PDF to various other image formats like PNG, BMP, SVG, and TIFF. For more details, refer to the documentation: Convert PDF to Image in C#.

Convert Multiple Pages (All or Range)

Convert All Pages

The following loop iterates over all pages, converts each one into an image, and saves it to disk with page numbers in the filename.

for (int i = 0; i < doc.Pages.Count; i++)
{
    Image image = doc.SaveAsImage(i, PdfImageType.Bitmap);
    string fileName = string.Format("Output\\ToJPG-{0}.jpg", i);
    image.Save(fileName, ImageFormat.Jpeg);
}

Convert a Range of Pages

To convert a specific range of pages (e.g., pages 2 to 4), modify the for loop as follows:

for (int i = 1; i <= 3; i++)
{
    Image image = doc.SaveAsImage(i, PdfImageType.Bitmap);
    string fileName = string.Format("Output\\ToJPG-{0}.jpg", i);
    image.Save(fileName, ImageFormat.Jpeg);
}

Advanced Conversion Options

Set Image Resolution/Quality

By default, the output resolution might be too low for printing or detailed analysis. You can set DPI explicitly:

Image image = doc.SaveAsImage(0, PdfImageType.Bitmap, 300, 300);
image.Save("ToJPG.jpg", ImageFormat.Jpeg);

Tips:

• 72 DPI : Default, screen quality.
• 150 DPI : Good for previews and web.
• 300 DPI : High quality, suitable for printing.

Higher DPI results in sharper images but also increases memory and file size.

Save the Converted Images as Stream

Instead of writing directly to disk, you can store the output in memory streams. This is useful in:

• ASP.NET applications returning images to browsers.
• Web APIs sending images as HTTP responses.
• Database storage for binary blobs.

using (MemoryStream ms = new MemoryStream())
{
    pdf.SaveAsImage(0, PdfImageType.Bitmap, 300, 300).Save(ms, ImageFormat.Jpeg);
    byte[] imageBytes = ms.ToArray();
}

Here, the JPG image is stored as a byte array , ready for further processing.

Batch Conversion (Multiple PDFs)

In scenarios where you need to process multiple PDF documents at once, you can apply batch conversion as shown below:

string[] files = Directory.GetFiles("InputPDFs", "*.pdf");
foreach (string file in files)
{
    PdfDocument doc = new PdfDocument();
    doc.LoadFromFile(file);
    for (int i = 0; i < doc.Pages.Count; i++)
    {
        Image image = doc.SaveAsImage(i, PdfImageType.Bitmap);
        string fileName = Path.GetFileNameWithoutExtension(file);
        image.Save($"Output\\{fileName}-Page{i + 1}.jpg", ImageFormat.Jpeg);
    }
    doc.Dispose();
}

Troubleshooting & Best Practices

Working with PDF-to-image conversion in .NET can come with challenges. Here’s how to address them:

1. Large PDFs consume memory
   • Use lower DPI (e.g., 150 instead of 300).
   • Process in chunks rather than loading everything at once.
2. Images are blurry or low quality
   • Increase DPI.
   • Consider using PNG instead of JPG for sharp diagrams or text.
3. File paths cause errors
   • Always check that the output directory exists.
   • Use Path.Combine() for cross-platform paths.
4. Handling password-protected PDFs
   • Provide the password when loading:

doc.LoadFromFile("secure.pdf", "password123");

1. Dispose objects
   • Always call Dispose() on PdfDocument and Image objects to release memory.

Conclusion

Converting PDF to JPG in .NET is straightforward with Spire.PDF for .NET . The library provides the SaveAsImage() method, allowing you to convert a single page or an entire document with just a few lines of code. With options for custom resolution, stream handling, and batch conversion , you can adapt the workflow to desktop apps, web services, or cloud platforms.

By following best practices like managing memory and adjusting resolution, you can ensure efficient, high-quality output that fits your project’s requirements.

If you’re exploring more advanced document processing, Spire also offers libraries for Word, Excel, and PowerPoint, enabling a complete .NET document solution.

FAQs

Q1. Can I convert PDFs to formats other than JPG?

Yes. Spire.PDF supports PNG, BMP, SVG, and other common formats.

Q2. What DPI should I use?

• 72 DPI for thumbnails.
• 150 DPI for web previews.
• 300 DPI for print quality.

Q3. Does Spire.PDF support encrypted PDFs?

Yes, but you need to provide the correct password when loading the file.

Q4. Can I integrate this in ASP.NET?

Yes. You can save images to memory streams and return them as HTTP responses.

Q5. Can I convert images back to PDF?

Yes. You can load JPG, PNG, or BMP files and insert them into PDF pages, effectively converting images back into a PDF.

Get a Free License

To fully experience the capabilities of Spire.PDF for .NET without any evaluation limitations, you can request a free 30-day trial license.

HTML is widely used to present content in web browsers, but preserving its exact layout when sharing or printing can be challenging. PDF, by contrast, is a universally accepted format that reliably maintains document layout across various devices and operating systems. Converting HTML to PDF is particularly useful in web development, especially when creating printable versions of web pages or generating reports from web data.

Spire.PDF for .NET now supports a streamlined method to convert HTML to PDF in C# using the ChromeHtmlConverter class. This tutorial provides step-by-step guidance on performing this conversion effectively.

• Convert HTML to PDF with ChromeHtmlConverter in C#
• Generate Output Logs During HTML to PDF Conversion in C#

Install Spire.PDF for .NET

To begin with, you need to add the DLL files included in the Spire.PDF for.NET package as references in your .NET project. The DLLs files can be either downloaded from this link or installed via NuGet.

PM> Install-Package Spire.PDF

Install Google Chrome

This method requires Google Chrome to perform the conversion. If Chrome is not already installed, you can download it from this link and install it.

Convert HTML to PDF using ChromeHtmlConverter in C#

You can utilize the ChromeHtmlConverter.ConvertToPdf() method to convert an HTML file to a PDF using the Chrome plugin. This method accepts 3 parameters, including the input HTML file path, output PDF file path, and ConvertOptions which allows customization of conversion settings like conversion timeout, PDF paper size and page margins. The detailed steps are as follows.

• Create an instance of the ChromeHtmlConverter class and provide the path to the Chrome plugin (chrome.exe) as a parameter in the class constructor.
• Create an instance of the ConvertOptions class.
• Customize the conversion settings, such as the conversion timeout, the paper size and page margins of the converted PDF through the properties of the ConvertOptions class.
• Convert an HTML file to PDF using the ChromeHtmlConverter.ConvertToPdf() method.

using Spire.Additions.Chrome;

namespace ConvertHtmlToPdfUsingChrome
{
    internal class Program
    {
        static void Main(string[] args)
        {
            //Specify the input URL and output PDF file path
            string inputUrl = @"https://www.e-iceblue.com/Tutorials/Spire.PDF/Spire.PDF-Program-Guide/C-/VB.NET-Convert-Image-to-PDF.html";            
            string outputFile = @"HtmlToPDF.pdf";

            //Specify the path to the Chrome plugin
            string chromeLocation = @"C:\Program Files\Google\Chrome\Application\chrome.exe";

            //Create an instance of the ChromeHtmlConverter class
            ChromeHtmlConverter converter = new ChromeHtmlConverter(chromeLocation);

            // Create an instance of the ConvertOptions class
            ConvertOptions options = new ConvertOptions();
            //Set conversion timeout
            options.Timeout = 10 * 3000;
            //Set paper size and page margins of the converted PDF
            options.PageSettings = new PageSettings()
            {
                PaperWidth = 8.27,
                PaperHeight = 11.69,
                MarginTop = 0,
                MarginLeft = 0,
                MarginRight = 0,
                MarginBottom = 0

            };

            //Convert the URL to PDF
            converter.ConvertToPdf(inputUrl, outputFile, options);
        }
    }
}

The converted PDF file maintains the same appearance as if the HTML file were printed to PDF directly through the Chrome browser:

Generate Output Logs During HTML to PDF Conversion in C#

Spire.PDF for .NET enables you to generate output logs during HTML to PDF conversion using the Logger class. The detailed steps are as follows.

• Create an instance of the ChromeHtmlConverter class and provide the path to the Chrome plugin (chrome.exe) as a parameter in the class constructor.
• Enable Logging by creating a Logger object and assigning it to the ChromeHtmlConverter.Logger property.
• Create an instance of the ConvertOptions class.
• Customize the conversion settings, such as the conversion timeout, the paper size and page margins of the converted PDF through the properties of the ConvertOptions class.
• Convert an HTML file to PDF using the ChromeHtmlConverter.ConvertToPdf() method.

using Spire.Additions.Chrome;

namespace ConvertHtmlToPdfUsingChrome
{
    internal class Program
    {
        static void Main(string[] args)
        {
            //Specify the input URL and output PDF file path
            string inputUrl = @"https://www.e-iceblue.com/Tutorials/Spire.PDF/Spire.PDF-Program-Guide/C-/VB.NET-Convert-Image-to-PDF.html";
            string outputFile = @"HtmlToPDF.pdf";

            // Specify the log file path
            string logFilePath = @"Logs.txt";

            //Specify the path to the Chrome plugin
            string chromeLocation = @"C:\Program Files\Google\Chrome\Application\chrome.exe";

            //Create an instance of the ChromeHtmlConverter class
            ChromeHtmlConverter converter = new ChromeHtmlConverter(chromeLocation);
            //Enable logging
            converter.Logger = new Logger(logFilePath);

            //Create an instance of the ConvertOptions class
            ConvertOptions options = new ConvertOptions();
            //Set conversion timeout
            options.Timeout = 10 * 3000;
            //Set paper size and page margins of the converted PDF
            options.PageSettings = new PageSettings()
            {
                PaperWidth = 8.27,
                PaperHeight = 11.69,
                MarginTop = 0,
                MarginLeft = 0,
                MarginRight = 0,
                MarginBottom = 0

            };

            //Convert the URL to PDF
            converter.ConvertToPdf(inputUrl, outputFile, options);
        }
    }
}

Here is the screenshot of the output log file:

Apply for a Temporary License

If you'd like to remove the evaluation message from the generated documents, or to get rid of the function limitations, please request a 30-day trial license for yourself.