CVImage and PixelFlow in Processing

import cvimage.*;
import processing.video.*;
import com.thomasdiewald.pixelflow.java.DwPixelFlow;
import com.thomasdiewald.pixelflow.java.fluid.DwFluid2D;
import org.opencv.core.*;
import org.opencv.objdetect.CascadeClassifier;
import org.opencv.objdetect.Objdetect;
 
// Face detection size
final int W = 320, H = 180;
Capture cap;
CVImage img;
CascadeClassifier face;
float ratio;
DwFluid2D fluid;
PGraphics2D pg_fluid;
MyFluidData fluidFunc;
 
void settings() {
  size(1280, 720, P2D);
}
 
void setup() {
  background(0);
  System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
  println(Core.VERSION);
  cap = new Capture(this, width, height);
  cap.start();
  img = new CVImage(W, H);
  face = new CascadeClassifier(dataPath("haarcascade_frontalface_default.xml"));
  ratio = float(width)/W;
 
  DwPixelFlow context = new DwPixelFlow(this);
  context.print();
  context.printGL();
  fluid = new DwFluid2D(context, width, height, 1);
  fluid.param.dissipation_velocity = 0.60f;
  fluid.param.dissipation_density = 0.99f;
  fluid.param.dissipation_temperature = 1.0f;
  fluid.param.vorticity = 0.001f;
 
  fluidFunc = new MyFluidData();
  fluid.addCallback_FluiData(fluidFunc);
  pg_fluid = (PGraphics2D) createGraphics(width, height, P2D);
  pg_fluid.smooth(4);
}
 
void draw() {
  if (!cap.available()) 
    return;
  background(0);
  cap.read();
  cap.updatePixels();
 
  img.copy(cap, 0, 0, cap.width, cap.height, 
    0, 0, img.width, img.height);
  img.copyTo();
 
  Mat grey = img.getGrey();
  MatOfRect faces = new MatOfRect();
 
  face.detectMultiScale(grey, faces, 1.15, 3, 
    Objdetect.CASCADE_SCALE_IMAGE, 
    new Size(60, 60), new Size(200, 200));
  Rect [] facesArr = faces.toArray();
  if (facesArr.length > 0) {
    fluidFunc.findFace(true);
  } else {
    fluidFunc.findFace(false);
  }
  for (Rect r : facesArr) {
    float cx = r.x + r.width/2.0;
    float cy = r.y + r.height/2.0;
    fluidFunc.setPos(new PVector(cx*ratio, cy*ratio));
  }
  fluid.update();
  pg_fluid.beginDraw();
  pg_fluid.background(0);
  pg_fluid.image(cap, 0, 0);
  pg_fluid.endDraw();
  fluid.renderFluidTextures(pg_fluid, 0);
  image(pg_fluid, 0, 0);
  pushStyle();
  noStroke();
  fill(0);
  text(nf(round(frameRate), 2, 0), 10, 20);
  popStyle();
  grey.release();
  faces.release();
}

private class MyFluidData implements DwFluid2D.FluidData {
  float intensity;
  float radius;
  float temperature;
  color c;
  boolean first;
  boolean face;
  PVector pos;
  PVector last;
 
  public MyFluidData() {
    super();
    intensity = 1.0f;
    radius = 25.0f;
    temperature = 5.0f;
    c = color(255, 255, 255);
    first = true;
    pos = new PVector(0, 0);
    last = new PVector(0, 0);
    face = false;
  }
 
  public void findFace(boolean f) {
    face = f;
  }
 
  public void setPos(PVector p) {
    if (first) {
      pos.x = p.x;
      pos.y = p.y;
      last.x = pos.x;
      last.y = pos.y;
      first = false;
    } else {
      last.x = pos.x;
      last.y = pos.y;
      pos.x = p.x;
      pos.y = p.y;
    }
  }
 
  @Override
    public void update(DwFluid2D f) {
 
    if (face) {
      float px = pos.x;
      float py = height - pos.y;
      float vx = (pos.x - last.x) * 10.0f;
      float vy = (pos.y - last.y) * -10.0f;
      c = color(random(100, 255), random(100, 255), random(50, 100));
      f.addVelocity(px, py, radius, vx, vy);
      f.addDensity (px, py, radius, 
        red(c)/255, green(c)/255, blue(c)/255, 
        intensity);
      f.addTemperature(px, py, radius, temperature);
    }
  }
}