is there a (simple) way to write objects into layer within a pdf ?

any hints ?
thanks
Floris

hack follows (shown as a per-sketch hack, build it as a library if you'd rather):

1.  browse thru the p5 libraries folder to find the source PGraphicsPDF.java
2.  copy that into your sketch folder as MyGraphicsPDF.java
3.  open the sketch, activate the MyGraphicsPDF.java tab
4.  delete the "package processing.pdf;" statement
5.  change the class name def and constructor from "P.." to "My.."
6.  add the following two functions at bottom of class:
 public void createAndBeginLayer(String name) {
   PdfLayer layer = new PdfLayer(name, writer);
   content.beginLayer(layer);
 }
 public void endLayer() {
   content.endLayer();
 }

When recording to pdf do something like this:
MyGraphicsPDF pdf;
pdf = (MyGraphicsPDF)beginRecord("MyGraphicsPDF", "out.pdf");

Then to draw stuff onto unique layers:

pdf.createAndBeginLayer("lines");
// draw some lines
pdf.endLayer();
pdf.createAndBeginLayer("circles");
// draw some circles
pdf.endLayer();
endRecord();

If you wanted to get fancier you could break apart createLayer() (returning a PdfLayer) and beginLayer(PdfLayer) so that you can interleave your drawing to various layers, but you'll also need a reference to the lowagie stuff in your sketch.

hth