R/split_from.R

In pridiltal/staplr: A Toolkit for PDF Files

#' Splits single input PDF document into parts from given points
#'
#' @description If the toolkit Pdftk is available in the
#' system, it will be called to Split a single input PDF document
#' into two parts from a given point
#'
#' See the reference for detailed usage of \code{pdftk}.
#' @param pg_num A vector of non-negative integers. Split the pdf document into parts from the numbered pages.
#' @inheritParams input_filepath
#' @param output_directory the path of the output directory
#' @param prefix A string for output filename prefix
#' @inheritParams overwrite
#' @inherit return return
#' @author Priyanga Dilini Talagala and Ogan Mancarci
#' @examples
#'
#' if (requireNamespace("lattice", quietly = TRUE)) {
#' dir <- tempfile()
#' dir.create(dir)
#' for(i in 1:4) {
#' pdf(file.path(dir, paste("plot", i, ".pdf", sep = "")))
#' print(lattice::xyplot(iris[,1] ~ iris[,i], data = iris))
#' dev.off()
#' }
#' staple_pdf(input_directory = dir, output_filepath = file.path(dir, 'Full_pdf.pdf'))
#' input_path <- file.path(dir, "Full_pdf.pdf")
#' split_from(pg_num=2, input_filepath = input_path ,output_directory = dir )
#' }
#' @export
#' @references \url{https://www.pdflabs.com/tools/pdftk-the-pdf-toolkit/}
split_from <- function(pg_num, input_filepath = NULL, output_directory = NULL, prefix = 'part',
                       overwrite = TRUE) {

  assertthat::assert_that(is.numeric(pg_num))

  if(is.null(input_filepath)){
    #Choose the pdf file interactively
    input_filepath <- file.choose(new = FALSE)
  }

  if(is.null(output_directory)){
    #Select a folder to store output
    output_directory<- tcltk::tk_choose.dir(caption = "Select directory to save output")
  }

  input_filepath <- normalizePath(input_filepath, mustWork = TRUE)
  output_directory <- normalizePath(output_directory, mustWork = TRUE)

  parts <- length(pg_num) + 1
  splitPoints <- c(0,pg_num,'end')
  digits <- floor(log(parts))

  for (i in seq_len(parts)){
    output_filepath <- file.path(output_directory,
                                 paste(prefix, stringr::str_pad(i,digits, pad = '0'),
                                       ".pdf",  sep = ""))

    if(!overwrite & file.exists(output_filepath)){
      stop(paste(output_filepath,'already exists. Set overwrite = TRUE to overwrite'))
    }

    system_command <- paste(pdftk_cmd(),
                            shQuote(input_filepath),
                            "cat",
                            paste(as.integer(splitPoints[i])+1,'-',splitPoints[i+1], sep = ""),
                            "output",
                            shQuote(output_filepath),
                            sep = " ")

    sys_out <- system(command = system_command)
  }

  if(sys_out == 0){
    return(TRUE)
  } else{
    return(FALSE)
  }

}