Snap filter

//@input float faceScale = 3.0 {"label":"Face scale", "min": 1.0, "max": 5.0, "step":0.1}
//@input float easeDuration = 0.5 {"label":"Zoom duration's)", "min": 0.1, "max": 10.0, "step":0.1}
//@input Component.Head head
//@input Component.Camera camera
//@input Component.Image image

var zoom = 0;
var endZoom = 0;
var startZoom = 0;
var isFaceTracking = false;
var startTime = 0;
function onFaceFound()
{
   isFaceTracking = true;
   startTime = getTime();
   startZoom = zoom;
}
function onFaceLost()
{
   isFaceTracking = false;
   startTime = getTime();
   startZoom = zoom;
}

function onUpdate()
{
    var top;
    var bottom;
    var center;
    var transform = script.image.getSceneObject().getComponent("Component.ScreenTransform");

   if(!isFaceTracking) {
        top    = new vec2(0,1);
        right  = new vec2(.5,.5);
        bottom = new vec2(0,-2);
        left  = new vec2(.5,.5);
        center = new vec2(0.5,0.5);
    }else{
        top    = script.head.getLandmark(71);
        right  = script.head.getLandmark(16);
        bottom = script.head.getLandmark(8);
        left   = script.head.getLandmark(0);
        center = script.head.getLandmark(29);
    }


    //Compute face height
    var faceSize = bottom.y - top.y;
    if(script.camera.aspect < 1) {
        faceSize = right.x - left.x;
    }

    //Set zoom so the face fits the screen (times the faceScale value)
    var endZoom = 1/faceSize * script.faceScale;

    //Reduce zoom scale on mobile vertical screens
    //if(script.camera.aspect < 1) endZoom /= 2;

    //Ease zoom value
    var elapsedDuration = Math.min(script.easeDuration, getTime()-startTime);
    var endValue = !isFaceTracking? 0 : endZoom;
    var func = !isFaceTracking? easeIn : easeOut
    zoom = func(elapsedDuration, startZoom, endValue-startZoom, script.easeDuration);

    //Compensate scale generated offset by panning
    var offsetX = (center.x - .5) * zoom;
    var offsetY = (center.y - .5) * zoom;

    //Move texture opposite to face position to center it.
    center.x = (-center.x*2+1) - offsetX;
    center.y = (center.y*2-1) + offsetY;

    //Avoid texture border to be visible
    if(center.x >= .5*zoom) center.x = .5*zoom;
    if(center.x <= -.5*zoom) center.x = -.5*zoom;
    if(center.y >= .5*zoom) center.y = .5*zoom;
    if(center.y <= -.5*zoom) center.y = -.5*zoom;

    //Move and scale texture
    transform.anchors.setCenter(center);
    transform.anchors.setSize(new vec2(zoom, zoom));

}

script.createEvent("FaceFoundEvent").bind(onFaceFound);
script.createEvent("FaceLostEvent").bind(onFaceLost);
script.createEvent("UpdateEvent").bind( onUpdate );

function easeOut(t, b, c, d, s) {
    return c * (t /= d) * t * t * t * t * t  + b;
};

function easeIn(t, b, c, d, s) {
    return c * ((t = t / d - 1) * t * t * t * t + 1) + b;
}