Document Similarity

Compare two images or PDFs for visual similarity via the PDFAPIHub cloud API. Documents are uploaded to pdfapihub.com for comparison using feature matching, SSIM, or perceptual hashing. Requires a CLIENT-API-KEY header.

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

Method	Description
auto	Automatically selects best method (default)
feature_match	OpenCV feature matching
ssim	Structural Similarity Index
phash	Perceptual 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"
  }'