I have code from Rapid-Android-Developmen book

saha

import ketai.camera.*;

KetaiCamera cam;
PImage bg, snapshot, mux;`

void setup() {
  fullScreen();
  orientation(LANDSCAPE);
  cam = new KetaiCamera(this, 1280, 768, 30);
  cam.setCameraID(1);  //(1)
  imageMode(CENTER);
  stroke(255);
  textSize(48);
  snapshot = createImage(1280, 768, RGB);
  bg = loadImage("rover.jpg");  //(2)
  bg.resize(1280, 768);
  bg.loadPixels();
  mux = new PImage(1280, 768);
}

void draw() 
{
  background(0);

  if (cam.isStarted()) {   
    cam.loadPixels();  //(3)
    snapshot.loadPixels();  //(4)
    mux.loadPixels();  //(5)

    for (int i= 0; i < cam.pixels.length; i++)
    {  
      color currColor = cam.pixels[i];  //(6)
      float currR = abs(red(cam.pixels[i]) - red(snapshot.pixels[i]) );  //(7)
      float currG = abs(green(cam.pixels[i]) - green(snapshot.pixels[i]));
      float currB = abs(blue(cam.pixels[i]) - blue(snapshot.pixels[i]));      
      float total = currR+currG+currB;  //(8)

      if (total < 128)
        mux.pixels[i] = bg.pixels[i];  //(9)   
      else
        mux.pixels[i] = cam.pixels[i];  //(10)

    }

    mux.updatePixels();  //(11)
    image(mux, width/2, height/2, width, height);  //(12)
  } 
  drawUI();
}

void drawUI()
{
  fill(0, 128);
  rect(0, 0, width/4, 100);
  rect(width/4, 0, width/4, 100);
  rect(2*(width/4), 0, width/4, 100);
  rect(3*(width/4), 0, width/4-1, 100);
  fill(255);

  if (cam.isStarted())
    text("stop", 20, 70);
  else
    text("start", 20, 70);

  text("camera", (width/4)+20, 70);
  text("snapshot", 2*(width/4)+20, 70);
}

void mousePressed()
{
  if (mouseY <= 100) {
    //start/stop the camera
    if (mouseX > 0 && mouseX < width/4)
    {
      if (cam.isStarted())
      {
        cam.stop();
      }
      else
      {
        if (!cam.start())
          println("Failed to start camera.");

        bg.resize(cam.width, cam.height);
      }
    }
    //switch cameras
    else if (mouseX > width/4 && mouseX < 2*(width/4))
    {
      int cameraID = 0;

      if (cam.getCameraID() == 0)
        cameraID = 1;
      else
        cameraID = 0;

      cam.stop();
      cam.setCameraID(cameraID);
      cam.start();
    }

    //take snapshot
    else if (mouseX > 2*(width/4) && mouseX < 3*(width/4))
    {
      cam.manualSettings(); //(1)   
      snapshot.copy(cam, 0, 0, cam.width, cam.height,0, 0, snapshot.width, snapshot.height);  //(2)
      mux.resize(cam.width, cam.height);
    }
  }
}

void onCameraPreviewEvent()
{  
  cam.read();
}

void exit() 
{
  cam.stop();
}

I have problem is

java.lang.RuntimeException: Camera is being used after Camera.release() was called at android.hardware.Camera.native_getParameters(Native Method) at android.hardware.Camera.getParameters(Camera.java:2007) at ketai.camera.KetaiCamera.start(KetaiCamera.java:480) at processing.test.cameraphotobooth.CameraPhotobooth.mousePressed(CameraPhotobooth.java:96) at processing.core.PApplet.mousePressed(Unknown Source) at processing.core.PApplet.handleMouseEvent(Unknown Source) at processing.core.PApplet.dequeueEvents(Unknown Source) at processing.core.PApplet.handleDraw(Unknown Source) at processing.core.PGraphicsAndroid2D.requestDraw(Unknown Source) at processing.core.PApplet.run(Unknown Source) at java.lang.Thread.run(Thread.java:818)

Thank you.