Question

Is there a way one could zoom and pan on a canvas using KineticJS? I found this library kineticjs-viewport, but just wondering if there is any other way of achieving this because this library seems to be using so many extra libraries and am not sure which ones are absolutely necessary to get the job done.

Alternatively, I am even open to the idea of drawing a rectangle around the region of interest and zooming into that one particular area. Any ideas on how to achieve this? A JSFiddle example would be awesome!

Answer 1

You can simply add .setDraggable("draggable") to a layer and you will be able to drag it as long as there is an object under the cursor. You could add a large, transparent rect to make everything draggable. The zoom can be achieved by setting the scale of the layer. In this example I’m controlling it though the mousewheel, but it’s simply a function where you pass the amount you want to zoom (positive to zoom in, negative to zoom out). Here is the code:

var stage = new Kinetic.Stage({
    container: "canvas",
    width: 500,
    height: 500
});

var draggableLayer = new Kinetic.Layer();
draggableLayer.setDraggable("draggable");

//a large transparent background to make everything draggable
var background = new Kinetic.Rect({
    x: -1000,
    y: -1000,
    width: 2000,
    height: 2000,
    fill: "#000000",
    opacity: 0
});

draggableLayer.add(background);


//don't mind this, just to create fake elements
var addCircle = function(x, y, r){
  draggableLayer.add(new Kinetic.Circle({
        x: x*700,
        y: y*700,
        radius: r*20,
        fill: "rgb("+ parseInt(255*r) +",0,0)"
    })
  );
}

var circles = 300
while (circles) {
  addCircle(Math.random(),Math.random(), Math.random())
  circles--;
}

var zoom = function(e) {
  var zoomAmount = e.wheelDeltaY*0.001;
  draggableLayer.setScale(draggableLayer.getScale().x+zoomAmount)
  draggableLayer.draw();
}

document.addEventListener("mousewheel", zoom, false)

stage.add(draggableLayer)

http://jsfiddle.net/zAUYd/