docs: public static String makeMarginTransform(double owidth, double oheight, double iwidth, double iheight, double lmargin, double tmargin, double rmargin, double bmargin) {
      double swidth = iwidth + lmargin + rmargin;
      double sheight = iheight + tmargin + bmargin;
      double scale = Math.max(swidth / owidth, sheight / oheight);
      double offx = (scale * owidth - swidth) * .5 + lmargin;
      double offy = (scale * oheight - sheight) * .5 + tmargin;
      return "scale(" + fmt(1 / scale) + ") translate(" + fmt(offx) + " " + fmt(offy) + ")";
    }