konva/test/unit/Canvas-test.js

suite('Canvas', function () {
  // ======================================================
  test('pixel ratio', function () {
    var stage = addStage();

    var layer = new Konva.Layer();

    var circle = new Konva.Circle({
      x: 100,
      y: 70,
      radius: 70,
      fill: 'green',
      stroke: 'blue',
      strokeWidth: 4,
      draggable: true,
    });

    layer.add(circle);
    stage.add(layer);

    stage.setWidth(578 / 2);
    stage.setHeight(100);

    stage.draw();
    assert.equal(
      layer.getCanvas().getPixelRatio(),
      Konva.pixelRatio || window.devicePixelRatio || 1
    );

    layer.getCanvas().setPixelRatio(1);
    assert.equal(layer.getCanvas().getPixelRatio(), 1);
    assert.equal(layer.getCanvas().width, 289);
    assert.equal(layer.getCanvas().height, 100);

    layer.getCanvas().setPixelRatio(2);
    assert.equal(layer.getCanvas().getPixelRatio(), 2);
    assert.equal(layer.getCanvas().width, 578);
    assert.equal(layer.getCanvas().height, 200);

    layer.draw();
  });
});