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Check the integrity of a PDF file

Source: R/general_check_pdf.R
check_pdf.Rd

Verify that a file exists, is non-empty, is identified as a PDF document, and can be successfully validated by pdftools when available. Optionally, the first page can also be rendered to perform a stronger integrity check.

Usage

check_pdf(file, use_pdftools = FALSE, warning = TRUE, render = FALSE)

Arguments

file

Character scalar. Path to a PDF file.

use_pdftools

Logical scalar. If FALSE (default), perform a basic check using file info and the PDF header signature ("%PDF-"). If TRUE, use pdftools for validation; if pdftools is not installed, the function falls back to the basic header check and issues a warning if "warning = TRUE".

warning

Logical scalar. If TRUE, issue a warning when "use_pdftools = TRUE" but pdftools is not installed. Has no effect when "use_pdftools = FALSE" or when pdftools is installed.

render

Logical scalar. If TRUE, additionally attempt to render the first page using pdftools::pdf_render_page(). Rendering provides a stronger integrity check but is slower than metadata validation alone. Only has an effect when "use_pdftools = TRUE".

Value

A logical scalar:

  • TRUE: The file exists, is non-empty, and either (a) its first five bytes match the %PDF- header signature (use_pdftools = FALSE), or (b) it can be successfully parsed by pdftools ("use_pdftools = TRUE").

  • FALSE: The file is missing, empty, not recognised as a PDF, fails the header check, cannot be parsed, or an error occurs during validation.

Details

The function is intended to detect missing, empty, truncated, or corrupted PDF files. When "use_pdftools = TRUE", validation is performed by attempting to read document metadata using pdftools::pdf_info().

Validation is performed in the following order:

  • Verify that the file exists and is non-empty.

  • Verify that the file type contains the string pdf according to file_type().

  • If "use_pdftools = FALSE" or pdftools is not installed: check that the first five bytes of the file match the %PDF- header signature.

  • If "use_pdftools = TRUE" and pdftools is installed: attempt to read PDF metadata using pdftools::pdf_info().

  • If render = TRUE (and "use_pdftools = TRUE"): additionally attempt to render the first page using pdftools::pdf_render_page(). Any R-level messages emitted during rendering are suppressed. Note that Poppler may also emit font diagnostic messages directly to C-level stderr; these bypass R's message system, are harmless, and cannot be suppressed from R.

    Successful validation indicates that the PDF structure is readable by the Poppler library used by pdftools. It does not guarantee that every page is visually correct, but it provides a strong indication that the file is not corrupted.

Author

Ahmed El-Gabbas

Examples

ecokit::load_packages(fs)

# Create a temporary invalid pdf file
invalid_file <- fs::file_temp(ext = "pdf")
fs::file_create(invalid_file)
check_pdf(invalid_file)
#> [1] FALSE

# Create a valid pdf file
valid_file <- fs::file_temp(ext = "pdf")
invisible({
  grDevices::pdf(valid_file)
  plot(1:10)
  grDevices::dev.off()
})
check_pdf(valid_file, render = TRUE)
#> [1] TRUE

# Clean up temporary files
fs::file_delete(c(invalid_file, valid_file))