touch 缩小放大后拖拽图片问题

1.touch.js插件只是用来捕获touch事件，捕获到之后要做什么操作由我们自己来决定。这样就可以进行放大缩小后图片的拖拽，进而可以看到放大后的全图。以下是代码：

参考案例：UI2\system\components\justep\touch\demo\touchjs

Model.prototype.pinch = function(event) {
		var me = this;
		var id = this.getIDByXID('pinch');
		var posData = me.comp("posData");
		var target = document.getElementById(id);
		touch.on('#' + id, 'touchstart', function(ev) {
			ev.target = target;
		});
		var initialScale = 1;
		touch.on('#' + id, 'pinch', function(ev) {
			currentScale = ev.scale - 1;
			currentScale = initialScale + currentScale;
			currentScale = currentScale > 4 ? 4 : currentScale;// 最大倍数2
			currentScale = currentScale < 1 ? 1 : currentScale;// 最小倍数1
			currentScale = currentScale < 1 ? 1 : currentScale;

			target.style.webkitTransform = 'scale(' + currentScale + ')';
		});

		touch.on('#' + id, 'pinchend', function(ev) {
			initialScale = currentScale;
		});

		var dx, dy;

		touch.on('#' + id, 'drag', function(ev) {
			var x = this;
			dx = dx || 0;
			dy = dy || 0;
			var offx = dx + ev.x * 0.5 + "px";
			var offy = dy + ev.y * 0.5 + "px";
			target.style.webkitTransform = "scale(" + initialScale + ")" + "translate3d(" + offx + "," + offy + ",0)";

		});

		touch.on('#' + id, 'dragend', function(ev) {
			dx += ev.x;
			dy += ev.y;
		});
	};

2.另外，还可以使用其他的第三方js类库实现拖拽能力，比如hammerjs

http://hammerjs.github.io/

http://bbs.wex5.com/forum.php?mod=viewthread&tid=193394