ng2-pdfjs-viewer显示PDF全黑问题求助：关联生成工具差异

Hey there, let's break down your problem and walk through practical explanations and solutions:

First, let's clarify two key points tied to your problem:

How PDF Generator Identifiers Are Determined #

PDF files embed metadata fields like Producer and Creator that tools like pdfjs (which ng2-pdfjs-viewer relies on) use to identify the generating software. These fields are written directly into the PDF when it's created—they're not inferred from the content itself.

The fact that the same Byte[] request sometimes returns PDFs labeled with different generators, plus the smaller file size of the black-screen PDFs, strongly suggests your REST endpoint isn't returning the same complete file every time. Likely culprits:

• Server-side caching that serves outdated/incomplete files
• Branching logic in your PDF generation pipeline that outputs different versions
• Network transmission issues causing partial file truncation (which explains the smaller size and broken rendering)

Why j&k DPU-X PDFs Show Up Black #

ng2-pdfjs-viewer depends on pdfjs's rendering engine, which has trouble with non-standard PDF structures. Some generators like j&k DPU-X might use proprietary compression, font embedding, or page stream formats that pdfjs can't parse correctly. The smaller file size confirms these are incomplete PDFs—missing critical page content data, hence the all-black display.

Let's tackle this step by step:

1. Validate REST Request/Response Consistency

   • Use tools like Postman to repeatedly call your endpoint, save each returned PDF, and compare their hash values (use md5sum or sha256sum commands). If hashes differ, your server is returning inconsistent files—investigate caching, generation logic, or storage pipelines to ensure full, identical PDFs are sent every time.
   • Check the Content-Length HTTP response header against your Byte[] length. A mismatch means the file was truncated during transmission, which you'll need to fix at the network or server level.

2. Modify PDF Metadata (If Necessary)
   If you confirm you're getting complete j&k DPU-X PDFs and just want to update their generator labels, you can modify the embedded metadata with a PDF processing library. Here's a quick example using PyPDF2 (Python):

   from PyPDF2 import PdfReader, PdfWriter
   
   reader = PdfReader("input.pdf")
   writer = PdfWriter()
   
   # Copy all pages from the original PDF
   for page in reader.pages:
       writer.add_page(page)
   
   # Overwrite metadata fields
   writer.add_metadata({
       "/Producer": "OmniPage CSDK 19",
       "/Creator": "OmniPage CSDK 19"
   })
   
   # Save the modified PDF
   with open("output.pdf", "wb") as output_file:
       writer.write(output_file)
   

   Note: This won't fix the black-screen issue—it only changes the label. The root problem is PDF structure compatibility, not the identifier itself.

3. Fix Rendering Compatibility

   • Update ng2-pdfjs-viewer and its underlying pdfjs library to the latest version. New releases often include fixes for edge-case PDF rendering issues.
   • If updating doesn't work, convert j&k DPU-X PDFs to a standard format on the backend using Ghostscript. This normalizes non-standard structures so pdfjs can render them properly:

     gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/default -dNOPAUSE -dBATCH -sOutputFile=standardized.pdf input.pdf
     

Start with verifying the consistency and completeness of your REST endpoint's PDF responses—this is the most critical step. The generator identifier is just a metadata label; the real issue lies in incomplete or non-standard PDF files causing rendering failures.

内容的提问来源于stack exchange，提问作者Kay