A modified version of the Buffer class suggested by chicoatomico to recreate the Picking library for Processing 2.0

Buffer.pde

import java.nio.IntBuffer;
import java.nio.ByteOrder;

public class Buffer extends PGraphics3D
{
  protected int current_color = 0;

  public Buffer(PApplet parent)
  {
    setParent(parent);
    setSize(parent.width, parent.height);
  }
  
  protected int getPixel(int x, int y) {
    IntBuffer pixelColorBuffer = IntBuffer.allocate(1);
    int[] testArray = new int[1];
    beginPixelsOp(OP_READ);
    try {
      // The readPixels() call in inside a try/catch block because it appears
      // that (only sometimes) JOGL will run beginDraw/endDraw on the EDT
      // thread instead of the Animation thread right after a resize. Because
      // of this the width and height might have a different size than the
      // one of the pixels arrays.
      pgl.readPixels(x, height - y, 1, 1, PGL.RGBA, PGL.UNSIGNED_BYTE, 
      pixelColorBuffer);
      
      
    } 
    catch (IndexOutOfBoundsException e) {
      // Silently catch the exception.
    }
    endPixelsOp();
    try {
      // Idem...
      //getIntArray(pixelBuffer, pixels);
      //nativeToJavaARGB(pixels, width, height);
      //getIntArray(pixelColorBuffer, testArray);
     
      testArray[0] = nativeToJavaARGB(pixelColorBuffer.get(0));
      
    } 
    catch (ArrayIndexOutOfBoundsException e) {
    }
    return testArray[0];
  }
  
  int nativeToJavaARGB(int pixelColor) {
    if (ByteOrder.nativeOrder() == ByteOrder.BIG_ENDIAN) { // RGBA to ARGB
      return (pixelColor & 0xff000000) |
             ((pixelColor >> 8) & 0x00ffffff);
    } else { // ABGR to ARGB
      return (pixelColor & 0xff000000) |
             ((pixelColor << 16) & 0xff0000) |
             (pixelColor & 0xff00) |
             ((pixelColor >> 16) & 0xff);
    }
  }
  
  @Override
    public boolean displayable() { 
    return true;
  }

  public void callCheckSettings() { 
    super.checkSettings();
  }

  @Override
    public void lights() {
  }

  @Override
    public void smooth() {
  }

  @Override
    public void fill(int arg) {
  }

  @Override
    public void fill(float arg) {
  }

  @Override
    public void fill(float arg, float arg_1) {
  }

  @Override
    public void fill(int arg, float arg_1) {
  }

  @Override
    public void fill(float arg, float arg_1, float arg_2) {
  }

  @Override
    public void fill(float arg, float arg_1, float arg_2, float arg_3) {
  }

  @Override
    public void stroke(int arg) {
  }

  @Override
    public void stroke(float arg) {
  }

  @Override
    public void stroke(float arg, float arg_1) {
  }

  @Override
    public void stroke(int arg, float arg_1) {
  }

  @Override
    public void stroke(float arg, float arg_1, float arg_2) {
  }

  @Override
    public void stroke(float arg, float arg_1, float arg_2, float arg_3) {
  }

  @Override
    public void textureMode(int arg) {
  }

  @Override
    public void texture(PImage arg) {
  }

  @Override
    public void vertex(float x, float y, float z, float u, float v) { 
    super.vertex(x, y, z);
  }

  @Override
    public void image(PImage arg, float arg_1, float arg_2) {
  }

  @Override
    public void image(PImage arg, float arg_1, float arg_2, float arg_3, float arg_4) {
  }

  @Override
    public void image(PImage arg, float arg_1, float arg_2, float arg_3, float arg_4, int arg_5, int arg_6, int arg_7, int arg_8) {
  }

  @Override
    protected void imageImpl(PImage image, float x1, float y1, float x2, float y2, int u1, int v1, int u2, int v2) {
  }

  public void setCurrentId(int i) 
  {
    // ID 0 to 16777214  => COLOR -16777215 to -1 (white)
    // -16777216 is black
    current_color = i - 16777215;
    super.fill(current_color);
  }

  public int getId(int x, int y)
  {

    // COLOR -16777216 (black) to -1 => ID -1 (no object) to 16777214 */
    
    int id = getPixel(x, y) + 16777215;
    return id;
  }
}