How to get all strokes/Rectangles which have been drawn on Frame by Graphics object?

Question

I am very new to Graphics2D and Frame library. I was trying out PDFRenderer(from PDFBox library) to draw the pdf on a Graphics2D object. Here is the code:

import java.awt.*;
import java.awt.event.*;
import java.io.File;
import java.io.IOException;

import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.rendering.PDFRenderer;
public class Example01 extends Frame {
  /**
   * Instantiates an Example01 object.
   **/
  public static void main(String args[]) {
    new Example01();
  }
  /**
   * Our Example01 constructor sets the frame's size, adds the
   * visual components, and then makes them visible to the user.
   * It uses an adapter class to deal with the user closing
   * the frame.
   **/
  public Example01() {
    //Title our frame.
    super("Java 2D Example01");
    //Set the size for the frame.
    setSize(1000,1000);
    //We need to turn on the visibility of our frame
    //by setting the Visible parameter to true.
    setVisible(true);
    //Now, we want to be sure we properly dispose of resources
    //this frame is using when the window is closed.  We use
    //an anonymous inner class adapter for this.
    addWindowListener(new WindowAdapter()
      {public void windowClosing(WindowEvent e)
         {dispose(); System.exit(0);}
      }
    );
  }
  /**
   * The paint method provides the real magic.  Here we
   * cast the Graphics object to Graphics2D to illustrate
   * that we may use the same old graphics capabilities with
   * Graphics2D that we are used to using with Graphics.
   **/
  public void paint(Graphics g) {
    Graphics2D g2d = (Graphics2D)g;
    try (PDDocument document = PDDocument.load(new File("C:\\Users\\prabhjot.rai\\Desktop\\xceligent\\9542899.pdf")))
    {
        PDFRenderer pdfRenderer = new PDFRenderer(document);
        pdfRenderer.renderPageToGraphics(1, g2d);
        System.out.println(g2d.getStroke());
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }


  }
}

What this does is, creates a frame in which I can see the whole pdf. I am trying to get the strokes drawn inside the frame - using the graphics object. How can I get those? I am open to use any library other than frame, since my method pdfRenderer.renderPageToGraphics(1, g2d) requires only a Graphics2D object.

Answer 1

I'm afraid this is not possible.

Graphics2D is an image based graphics tool, meaning that all actions you take are drawn to the image and forgotten, only the resulting pixels are stored.

The function getStroke() only return the current stroke, which will be used when you use any of the draw methods.

Many grahpics frameworks take a different approach (such as JavaFX), which supports drawing shapes and figures in a node based way, allowing you to decompose and change parts of the image (this renders the actual image after each change).