R/import.R

In sjp/grImport2: Importing Vector Graphics

readPicture <- function(file, warn = TRUE) {
    if (missing(file))
        stop("'file' must be a character string representing a path to a file.")
    doc <- xmlParse(file)
    checkValidSVG(doc, warn = warn)
    svgImage <- xmlRoot(doc)
    pictureDims <- getPictureDims(svgImage)
    # Need to create picture definitions table first
    picdefs <- parsePictureDefinitions(svgImage)
    # Stick defs in .grImport2Env so can be modded on-the-fly during parseImage
    assign("defs", picdefs, envir=.grImport2Env)
    # Now parse the contents of the image (<defs> are ignored).
    # <use>s are resolved to "real" elements
    pic <- parseImage(xmlChildren(svgImage, addNames = FALSE),
                      picdefs, createDefs = FALSE)
    # Update defs for changes during parseImage
    picdefs <- get("defs", picdefs, envir=.grImport2Env)
    new("Picture",
        content = pic,
        defs = picdefs,
        summary = new("PictureSummary",
                      xscale = c(0, pictureDims[1]),
                      yscale = c(pictureDims[2], 0)))
}

checkValidSVG <- function(doc, minVersion = NA, warn = TRUE) {
    if (xmlName(xmlRoot(doc)) != "svg")
        stop("This picture is not an SVG document.")
    if (! warn)
        return()
    # Note: suppressing warnings because we know we just want comments
    # and do not care about the namespace (SVG) that they belong in
    grConvertComment <-
        suppressWarnings(getNodeSet(doc, "//comment()"))
    warningText <- 
        "This picture was not generated by the 'grConvert' package, errors may result"
    if (! length(grConvertComment) ||
        ! grepl("Created by grConvert", xmlValue(grConvertComment[[1]])))
        warning(warningText)
    # Future proofing on grConvert input, add a min version check on
    # the output that grConvert creates.
    if (! is.na(minVersion)) {
        grConvertComment <- xmlValue(grConvertComment[[1]])
        # Collect the version number (of the form v0.1-0, for example)
        fileVersion <-
            gsub(".*v([0-9.-]+) $", "\\1", grConvertComment, perl = TRUE)
        if (package_version(fileVersion) < package_version(minVersion))
            warning(paste0("This picture was generated by an old version of 'grConvert'. ",
                           "The minimum supported version is ", minVersion,". ",
                           "Errors may result"))
    }
}