Overcoming the size limit of base64 strings in Power BI: Leveraging Ghostscript with PDF Viewer

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Written by danielsallander

Introduction

Sometimes users encounter a challenge when dealing with large PDF files. Power BI has an upper string limit of 2.1 million characters, as describe in this post by Chris Webb. This post explores a solution: using Ghostscript in conjunction with Power BI’s custom visual, “PDF Viewer,” to efficiently manage and display large PDF files.

What is Ghostscript?

Ghostscript is an open-source interpreter for PostScript and PDF files. It is widely used for file conversion, processing, and optimization tasks. In our context, it plays a crucial role in reducing the size of PDF files, making them more manageable for Power BI.

Why Optimize PDF Size for Power BI?

Power BI’s custom visual “PDF Viewer” allows users to display PDF files within their reports. However, the 2.1 million character limit can be a significant hurdle. Large PDFs, especially those with high-resolution images or extensive data, can easily surpass this limit, rendering them unusable in Power BI. By optimizing these PDFs, we ensure they load efficiently and comply with Power BI’s limitations.

Step-by-Step Guide: Using Ghostscript to Optimize PDFs for Power BI

Step 1: Install Ghostscript

Start by downloading and installing Ghostscript. It’s available for multiple operating systems and can be downloaded from Ghostscript’s official website.

Step 2: Optimize the PDF

Once Ghostscript is installed, use it to reduce the size of your PDF. Here’s a basic command to do this:

gswin64c -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/screen -dNOPAUSE -dQUIET -dBATCH -sOutputFile="output.pdf" "pdf-large.pdf"

This command reduces the PDF size by adjusting the quality and compatibility level.

Step 3: Use the Optimized PDF in Power BI

With the optimized PDF, you can now use it in Power BI’s “PDF Viewer” custom visual. Simply convert to base64 and load the PDF as you would normally, and it should now comply with the character limit.

Benefits of Using Ghostscript with Power BI

  • Efficiency: Reduces loading times and improves performance in Power BI reports.
  • Compliance with Limits: Ensures PDFs stay within the 2.1 million character limit of Power BI.
  • Quality Maintenance: Ghostscript offers various settings to balance size reduction with quality retention.

Conclusion

Integrating Ghostscript with Power BI’s “PDF Viewer” custom visual presents an effective solution for managing large PDF files in Power BI. By reducing the size of these files, users can circumvent the character limit issue while maintaining the integrity and usefulness of their data.

Thanks to Greg Guidarelli for bringing this technique to my attention!

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