R/convertGraph.R

In convertGraph: Convert Graphical Files Format

#' @title Convert Graphical Files Format
#' @keywords graphics plot diagram literate visualization SVG PDF PNG JPEG BMP GIF
#' @usage convertGraph(from, to, size = 1.0, path = NULL)
#' @return Converts the given graphical file to the specified file format.
#'
#' @description Converts graphical file formats (SVG, PNG, JPEG, BMP, GIF, PDF, etc) to one another. The exceptions are the SVG file format that can only be converted to other formats and in contrast, PDF format, which can only be created from others graphical formats. The main purpose of the package was to provide a solution for converting SVG file format to PNG which is often needed for exporting graphical files produced by R widgets.
#'
#' @param from The graphical source file
#' @param to The file name and extension of the converted file
#' @param size Enlarge the converted graphical file by magnifying its resolution with the given number
#' @param path Path to executable 'phantomJS' binary, downloadble from \url{http://phantomjs.org/download.html}
#'
#' @author E. F. Haghish \cr
#' Medical Informatics and Biostatistics (IMBI) \cr
#' University of Freiburg, Germany \cr
#' \email{haghish@imbi.uni-freiburg.de} \cr
#' \cr
#' Department of Mathematics and Computer Science \cr
#' University of Southern Denmark \cr
#' \email{haghish@imada.sdu.dk}
#'
#'
#' @examples
#' \dontrun{
#' #convert SVG to PNG
#' convertGraph("./example.svg", "./example.png", path = "path to executable phantomJS" )
#'
#' #convert PNG to JPEG
#' convertGraph("./example.png", "./example.jpeg", path = "path to executable phantomJS" )
#'
#' #convert JPEG to PDF
#' convertGraph("./example.jpeg", "./example.pdf", path = "path to executable phantomJS" )
#' }
#'
#' @export
#' @importFrom tools file_path_as_absolute
#' @importFrom tools file_ext





convertGraph <- function(from, to, size = 1.0, path = NULL) {
    #, setup = FALSE
    #, width = 600, height = 450  #removed arguments

    # ---------------------------------------------------------
    # SYNTAX PROCESSING
    #   - check the arguments
    #   - if "path" is specified, memorize it
    #   - if "path" is not specified, try to access the last absolute path
    #   - else require 'phantomJS' with an error
    # =========================================================
    if (!is.null(path)) {
        if (file.exists(path)) {
            path <- file_path_as_absolute(path)
            memory <- system.file("PATHMEMORY", package = "convertGraph")
            write(path, file=memory, append=TRUE)
        }
    }
    else {
        memory <- system.file("PATHMEMORY", package = "convertGraph")
        read <- readLines(memory)
        if (length(read) > 0) {
            path <- read[length(read)]
            file.exists(path)
            #warnings(paste('the path to phantomJS was retreived from your ',
            # "latest defined path which is:\n", path))
        }
        else {
            err <- paste("'phantomJS' was not specified. Download phantomJS",
            "from 'http://phantomjs.org/download.html' and specify the path to",
            "executable binary...")
            stop(err)
        }
    }

    # ---------------------------------------------------------
    # PREPARE THE FILES
    #   - catch the JS commands
    #   - check for magnification and if it specified, create an html file
    #   - execute 'phantomJS' script
    #   -
    # =========================================================
    command <- system.file("lib/command.js", package = "convertGraph")
    phantomJS <- paste("'", file_path_as_absolute(path), "'", sep = "")

    #if (width != 600 | height != 450) {
    #    src <- system.file("lib/command.js", package = "convertGraph")
    #    command <- tempfile(pattern = "command", tmpdir = tempdir(), fileext = ".js")
    #    file.copy(src, command)
    #    write(paste("page.viewportSize = { width: ", width, ", height:", height,
    #        "};"), file=command, append=TRUE)
    #}

    if (size > 1.0) {
        from <- file_path_as_absolute(from)
        html <- tempfile(pattern = "file", tmpdir = tempdir(), fileext = ".html")
        content <- paste('<!doctype html>\n<head>\n<style type="text/css">\n
            body {zoom: ', size,';}\n</style>\n</head>\n<body>\n
            <img src="', from, '" />\n</body>\n</html>\n', sep = "")
        write(content, file=html, append=TRUE)
        phantomScript <- paste(phantomJS, command, html, to, sep = " ")
    }
    else {
        phantomScript <- paste(phantomJS, command, from, to, sep = " ")
    }
    system(phantomScript)
}