comparepdf

comparepdf helps you identify differences between two PDF files. The package is built for a golden-reference workflow against code that generates PDF reports:

1. Start from your clean or main branch.
2. Generate a PDF before making code changes. This is your golden reference.
3. Make changes to the code that produces the PDF.
4. Generate a new PDF.
5. Compare the two PDFs with compare_pdf().

Under the hood, comparepdf renders each PDF page to an image, performs an image diff page by page, and writes a self-contained HTML report.

Install

Install from GitHub with remotes:

install.packages("remotes")
remotes::install_github("Analyticsphere/comparepdf")

Use

library(comparepdf)

compare_pdf(
  ref_pdf = "/path/to/golden-reference-file.pdf",
  new_pdf = "/path/to/updated-file.pdf",
  report_path = "/path/to/pdf_comparison_report.html",
  dpi = 300,
  fuzz = 0
)

Replace /path/to/ and the example file names above with the appropriate paths and file names on your local machine.

The resulting comparision HTML report can have any name, although it must end in .html; pdf_comparison_report.html is only used as example. Note that the package will overwrite the HTML report file if you run compare_pdf() more than once with the same report_path.

PDF-to-image quality, and comparison strictness, can be changed with the dpi and fuzz settings, respectively. For consistent PDF comparisons, dpi = 300 and fuzz = 0 should be used. Decreasing dpi or increasing fuzz may reduce false positives and decrease runtime, but may result in false negatives.

What compare_pdf() does

• Takes a reference PDF and a new PDF.
• Compares matching pages at the pixel level.
• Writes an HTML report to the path and file name specified in report_path.

HTML report output

The HTML report is the main output users need:

• A summary showing whether the PDFs match.
• A warning if the two PDFs have different page counts.
• For each differing page, side-by-side images of the reference page, the new page, and the diff image.
• A self-contained file that can be shared or opened locally in a browser.

In interactive R sessions, the report is also opened in your browser automatically.