Question

我正在尝试在画布上设置简单的放大/缩小功能。我正在使用KineticJS来处理触摸事件和绘制画布，但无法实现缩放。 KinteicJS有一个类似的例子，但他们总是放大中心，而我有兴趣放大手指之间的点。

谢谢！

Answer 1

我为一个项目写的综合样本显示：
- 使用滚轮
在桌面上围绕鼠标点进行缩放 - 使用crossbrowser scrollwheel，包括firefox（使用jquery.mousewheel.js）
- iPAD使用手指之间的夹点进行缩放 - 支持iPAD方向更改和禁用safari自动缩放
- 在保持其他图层未缩放的同时缩放一个图层 - OOP javascript'class'和代理事件到本地方法

<!DOCTYPE html>
<html>
<head>
  <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  <script src="http://d3lp1msu2r81bx.cloudfront.net/kjs/js/lib/kinetic-v4.7.4.min.js"></script>
  <script src="http://code.jquery.com/jquery-1.10.2.min.js"></script>
  <script src="https://rawgithub.com/brandonaaron/jquery-mousewheel/master/jquery.mousewheel.js"></script>
</head>
<body>
  <div id="container"></div>

<script type='text/javascript'>
function makePos(x, y) {
    return {
        'x': x,
        'y': y
    };
}


function View() {
    this.init = init;

    var self = this;

    var kineticStage,
        kineticLayer,
        kineticTextLayer,

        zoomOrigin = makePos(0, 0),
        zoomFactor = 1.1,
        pinchLastDist, pinchStartCenter;

    init();

    function init() {

        // disable ipad zoom to prevent safari from zooming on orientation change
        $('head meta[name=viewport]').remove();
        $('head').prepend('<meta name="viewport" content="user-scalable=no, width=device-width, minimum-scale=1.0 , initial-scale=1.0, maximum-scale=1.0" />');

        // create stage layer and circle
        kineticStage = new Kinetic.Stage({
            container: 'container',
            width: $(document).width() - 10,
            height: $(document).height() - 10,
        });

        kineticLayer = new Kinetic.Layer({
            draggable: true
        });
        var circle = new Kinetic.Circle({
            x: 200,
            y: 200,
            radius: 50,
            fill: '#00D200',
            stroke: 'black',
            strokeWidth: 2,
        });
        kineticLayer.add(circle);
        kineticStage.add(kineticLayer);

        kineticTextLayer = new Kinetic.Layer({});
        kineticStage.add(kineticTextLayer);

        // register events and proxy to methods
        $(kineticStage.content).on('mousewheel', function(e) {
            e.preventDefault();
            var evt = e.originalEvent;
            stageMouseWheel.call(self, evt.deltaY, makePos(evt.clientX, evt.clientY));
        });
        kineticStage.getContent().addEventListener('touchmove', function(e) {
            e.preventDefault(); // prevent iPAD panning
            var touch1 = e.touches[0];
            var touch2 = e.touches[1];
            if (touch1 && touch2) {
            touch1.offsetX = touch1.pageX - $(touch1.target).offset().left;
            touch1.offsetY = touch1.pageY - $(touch1.target).offset().top;
            touch2.offsetX = touch2.pageX - $(touch2.target).offset().left;
            touch2.offsetY = touch2.pageY - $(touch2.target).offset().top;
            stagePinch.call(self, makePos(touch1.offsetX, touch1.offsetY), makePos(touch2.offsetX, touch2.offsetY));
            }
        }, false);
        kineticStage.getContent().addEventListener('touchend', function(e) {
            stageTouchEnd.call(self);
        }, false);

        $(window).on("orientationchange", function(event) {
            window.scrollTo(0, 0); // scroll to top left on orientation change
        });

        editTextLayer('scrollwheel/pinch to zoom');
        window.scrollTo(0, 0);
    }

    function zoom(newscale, center) { // zoom around center
        var mx = center.x - kineticLayer.getX(),
            my = center.y - kineticLayer.getY(),
            oldscale = kineticLayer.getScaleX();
        editTextLayer('zoom ' + newscale.toFixed(2) + ' around ' + mx.toFixed(2) + ',' + my.toFixed(2));

        zoomOrigin = makePos(mx / oldscale + zoomOrigin.x - mx / newscale, my / oldscale + zoomOrigin.y - my / newscale);

        kineticLayer.setOffset(zoomOrigin.x, zoomOrigin.y);
        kineticLayer.setScale(newscale);
        kineticLayer.draw();
    }

    function stageMouseWheel(factor, p) {
        var oldscale = kineticLayer.getScaleX(),
            newscale = oldscale * (zoomFactor - (factor < 0 ? 0.2 : 0));
        zoom(newscale, p);
    }

    function stagePinch(p1, p2) {
        var dist = Math.sqrt(Math.pow((p2.x - p1.x), 2) + Math.pow((p2.y - p1.y), 2));
        if (!pinchLastDist) pinchLastDist = dist;
        var newscale = kineticLayer.getScale().x * dist / pinchLastDist;

        var center = makePos(Math.abs((p1.x + p2.x) / 2), Math.abs((p1.y + p2.y) / 2));
        if (!pinchStartCenter) pinchStartCenter = center;

        zoom(newscale, pinchStartCenter);
        pinchLastDist = dist;
    }

    function stageTouchEnd() {
        pinchLastDist = pinchStartCenter = 0;
    }

    function editTextLayer(text) {
        var label = new Kinetic.Text({
            x: 0,
            y: 0,
            text: text,
            fontSize: 12,
            fontFamily: 'Calibri',
            fill: 'black'
        });

        kineticTextLayer.destroyChildren();
        kineticTextLayer.add(label);
        kineticTextLayer.drawScene();
    }
}


$(window).load(function() {
    var view = new View();
}); 
</script>

</body>
</html>

http://jsfiddle.net/45YJH/1/

Answer 2

对于那些仍然感兴趣的人，我们可以在画布上使用kineticJS进行缩放和平移。

http://jsfiddle.net/v1r00z/ZJE7w/

捏缩放画布

2 个答案: