R/split_merge.R

In leeper/tabulizer: Extract tables from PDF documents

#' @rdname split_merge
#' @title Split and merge PDFs
#' @description Split PDF into separate pages or merge multiple PDFs into one.
#' @param file For \code{merge_pdfs}, a character vector specifying the path to
#' one or more \emph{local} PDF files. For \code{split_pdf}, a character string
#' specifying the path or URL to a PDF file.
#' @param outdir For \code{split_pdf}, an optional character string specifying a
#' directory into which to split the resulting files. If \code{NULL}, the
#' \code{outdir} is \code{tempdir()}. If \code{file} is a URL, both the original
#' file and separate pages are stored in the R session's temporary directory.
#' @param outfile For \code{merge_pdfs}, a character string specifying the path
#' to the PDF file to create from the merged documents.
#' @param password Optionally, a character string containing a user password to
#' access a secured PDF. Currently, encrypted PDFs cannot be merged with
#' \code{merge_pdfs}.
#' @param copy Specifies whether the original local file(s) should be copied to
#' \code{tempdir()} before processing. \code{FALSE} by default. The argument is
#' ignored if \code{file} is URL.
#' @details \code{\link{split_pdf}} splits the file listed in \code{file} into
#' separate one-page doucments. \code{\link{merge_pdfs}} creates a single PDF
#' document from multiple separate PDF files.
#' @return For \code{split_pdfs}, a character vector specifying the output file
#' names, which are patterned after the value of \code{file}. For
#' \code{merge_pdfs}, the value of \code{outfile}.
#' @author Thomas J. Leeper <thosjleeper@gmail.com>
#' @examples
#' \dontrun{
#' # simple demo file
#' f <- system.file("examples", "data.pdf", package = "tabulapdf")
#' get_n_pages(file = f)
#'
#' # split PDF by page
#' sf <- split_pdf(f)
#'
#' # merge pdf
#' mf <- file.path(tempdir(), "merged.pdf")
#' merge_pdfs(sf, mf)
#' get_n_pages(mf)
#' }
#' @seealso \code{\link{extract_areas}}, \code{\link{get_page_dims}},
#' \code{\link{make_thumbnails}}
#' @importFrom rJava J new
#' @importFrom tools file_path_sans_ext
#' @export
split_pdf <- function(file,
                      outdir = NULL,
                      password = NULL,
                      copy = FALSE) {
    file <- localize_file(file, copy = copy)
    pdfDocument <- load_doc(file, password = password)
    on.exit(pdfDocument$close())
    splitter <- new(J("org.apache.pdfbox.multipdf.Splitter"))
    splitArray <- splitter$split(pdfDocument)
    iterator <- splitArray$iterator()
    p <- 1L

    fileseq <- formatC(1:splitArray$size(), width = nchar(splitArray$size()), flag = 0)
    if (is.null(outdir)) {
        outdir <- tempdir()
    }
    filename <- paste0(file_path_sans_ext(basename(file)), fileseq, ".pdf")
    outfile <- normalizePath(file.path(outdir, filename), mustWork = FALSE)

    while (.jcall(iterator, "Z", "hasNext")) {
        doc <- .jcall(iterator, "Ljava/lang/Object;", "next")
        doc$save(outfile[p])
        doc$close()
        p <- p + 1L
        rm(doc)
    }
    outfile
}

#' @rdname split_merge
#' @export
merge_pdfs <- function(file, outfile, copy = FALSE) {
    outfile <- normalizePath(outfile, mustWork = FALSE)
    file <- unlist(lapply(file, localize_file, copy = copy))
    merger <- new(J("org.apache.pdfbox.multipdf.PDFMergerUtility"))
    merger$setDestinationFileName(outfile)
    lapply(file, merger$addSource)
    merger$mergeDocuments()
    outfile
}