Opened PDFs not displaying correctly

[the-mitr]

Hi,

I have Mac OS 15.6 and installed I am using PDF Stirling 2.1.5 via java -jar ~/Downloads/Stirling-PDF.jar . The application opens properly at http://localhost:8080/ . But when I am opening any pdf file (either made from scanned images or direct electronic pdf from pandoc/docx etc.) the pages are not displaying at all. Instead of text on a white background I am getting coloured lines on all the pages. See the screenshot attached. The files open normally/correctly on other pdf viewers such as Preview / Skim/ Okular etc.
What could be the issue?

[dosubot[bot]]

Hi @the-mitr! I'm Dosu and I’m helping the Stirling-PDF team.

The colored lines you're seeing instead of proper PDF content in Stirling-PDF are most often caused by font rendering or memory issues in the PDF rendering engine. This can happen if the PDFs reference fonts (like Helvetica) that aren't embedded, or if the rendering DPI is set too high, causing memory errors—especially with large or image-heavy PDFs. Stirling-PDF's frontend recently switched to using a local pdfium WebAssembly module, which can be stricter about font embedding and memory limits than other viewers like Preview or Okular source.

Here are some steps to help isolate and potentially fix the issue:

1. Check your Java version: Run java --version in Terminal. Java 21 is recommended for best compatibility source.
2. Try a simple PDF: Open a one-page, text-only PDF to see if the issue persists. If it displays correctly, the problem may be with large images or high DPI settings.
3. Lower the rendering DPI: High DPI can cause memory errors and rendering artifacts like colored lines. If you have access to configuration, set the maximum DPI to 150 or less, or try processing smaller PDFs source.
4. Check for errors: Look for any warnings or errors in the Terminal where Stirling-PDF is running and in your browser's developer console when opening a PDF.
5. Font embedding: If your PDFs use non-embedded fonts, try converting them to PDF/A using Stirling-PDF's "Convert to PDF/A" tool. This can embed fonts and repair encoding, though it has limitations for some scripts source.

If none of these steps resolve the issue, try running Stirling-PDF with a different Java version or on another machine to see if the problem is environment-specific. If you spot any specific error messages or patterns, sharing those details can help pinpoint the cause.

To reply, just mention @dosu.

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