Document Similarity#

What It Does#

Compares two documents (images or PDFs) for visual similarity via the PDFAPIHub hosted API. Both documents are uploaded to PDFAPIHub servers where comparison is performed, and a similarity score (0–1) with confidence level is returned.

When to Use#

• Check if two documents are visually similar
• Detect duplicates or near-duplicates
• Compare image variations

Comparison Methods#

MethodDescriptionautoAutomatically selects best method (default)feature_matchOpenCV feature matchingssimStructural Similarity IndexphashPerceptual hashing

Supported Combinations#

• image + image
• pdf + pdf
• image + pdf

Required Inputs#

Two files via one of:

• url1 + url2 — public URLs
• image1_base64 + image2_base64 — base64-encoded files
• Multipart upload with file1 and file2

Authentication#

This skill calls the PDFAPIHub hosted API at https://pdfapihub.com/api. Both documents are uploaded to PDFAPIHub servers for comparison.

Send your API key in the CLIENT-API-KEY header.

Get your free API key at https://pdfapihub.com. Full API documentation is available at https://pdfapihub.com/docs.

Privacy note: Both documents you compare are uploaded to PDFAPIHub's cloud service for processing. Do not send confidential documents unless you trust the service. Files are auto-deleted after 30 days.

Use Cases#

• Duplicate Detection — Identify duplicate or near-duplicate documents in a repository
• Brand Consistency — Compare generated documents against approved templates for visual consistency
• QA Testing — Compare rendered PDFs/images before and after code changes for regressions
• Fraud Detection — Compare submitted documents against known genuine samples
• Document Versioning — Quantify visual differences between document revisions
• Container Inspection — Compare shipping container photos for damage assessment

Example Usage#

bash

curl -X POST https://pdfapihub.com/api/v1/document/similarity \
  -H "CLIENT-API-KEY: your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "url1": "https://pdfapihub.com/sample-document-similarity-1.jpg",
    "url2": "https://pdfapihub.com/sample-document-similarity-2.jpg",
    "method": "auto"
  }'