R function to convert all PDFs in a directory into PNGs

convert_pdf_to_png.R

#===============================================================================
# 2023-12-21 -- misc
# convert pdf to png
# Ilya Kashnitsky, ilya.kashnitsky@gmail.com, @ikashnitsky
#===============================================================================


#' @description A function to convert all PDFs in a directory into PNGs, or just one if specified.
#' @param dir_pdfs character. A character string with a path to the directory containing PDFs to convert
#' @param output_dir character. An optional parameter to specify the output directory for the converted PNGs. Defaults to `"/png"`.
#' @param pdf_name character. An optional parameter specifying the name of a single PDF file to convert (e.g., "01-part-to-whole.pdf"). Defaults to NULL.
convert_pdf_to_png <- function(dir_pdfs, output_dir = "/png", pdf_name = NULL) {
  
  require(pdftools)
  require(fs)
  require(magrittr)
  require(stringr)
  require(purrr)
  
  pdfs <- dir_ls(dir_pdfs) %>%
    str_subset("\\.pdf$")
  
  # If a specific PDF name is provided, filter the list
  if (!is.null(pdf_name)) {
    pdfs <- pdfs[str_detect(pdfs, fixed(pdf_name))]
    
    if (length(pdfs) == 0) {
      stop(paste("The specified file", pdf_name, "was not found in", dir_pdfs))
    }
  }
  
  if (length(pdfs) == 0) {
    message("No PDFs found to convert.")
    return(invisible(NULL))
  }
  
  base <- pdfs[1] %>% 
    str_remove("/[^/]+$")
  
  if(output_dir == "/png"){
    
    dir_create(path = paste0(base, "/png"))
    
    convert_one_pdf <- function(path_to_pdf){
      path = path_to_pdf %>% paste
      pdf_convert(
        pdf = path, 
        filenames = path %>% 
          str_remove(base) %>% 
          str_replace("\\.pdf$", ".png") %>% 
          paste0(base, "/png", .), 
        dpi = 300
      )
    }
    
  } else {
    convert_one_pdf <- function(path_to_pdf){
      path = path_to_pdf %>% paste
      pdf_convert(
        pdf = path, 
        filenames = path %>% 
          str_remove(base) %>% 
          str_replace("\\.pdf$", ".png") %>% 
          paste0(output_dir %>% path_expand %>% paste, .), 
        dpi = 300
      )
    }
  }
  
  pdfs %>% map(convert_one_pdf)
  
}