AngularJS 仿微信图片手势缩放的实例

angularjs 仿微信图片手势缩放的实例

前言：

最近，公司做一个混合应用项目，涉及到一个图片缩放功能，类似微信那样支持touch事件。

亲测，实现方案很不错，所以放出来，和大家分享一下，希望有人能用得到。

核心思想就是用到了css3的transform属性， 不多说，我们看代码：

'use strict';

/**
 * @nginject
 */
module.exports = function () {
  var _directive = {
    restrict : 'a',
    scope  : false,
    link   : _link
  };

  function _link(scope, element, attrs) {
    var elwidth, elheight;

    // mode : 'pinch' or 'swipe'
    var mode = '';

    // distance between two touche points (mode : 'pinch')
    var distance = 0;
    var initialdistance = 0;

    // image scaling
    var scale = 1;
    var relativescale = 1;
    var initialscale = 1;
    var maxscale = parseint(attrs.maxscale, 10);
    if (isnan(maxscale) || maxscale <= 1) {
      maxscale = 3;
    }

    // position of the upper left corner of the element
    var positionx = 0;
    var positiony = 0;

    var initialpositionx = 0;
    var initialpositiony = 0;

    // central origin (mode : 'pinch')
    var originx = 0;
    var originy = 0;

    // start coordinate and amount of movement (mode : 'swipe')
    var startx = 0;
    var starty = 0;
    var movex = 0;
    var movey = 0;

    var image = new image();
    image.onload = function() {
      elwidth = element[0].clientwidth;
      elheight = element[0].clientheight;

      element.css({
        '-webkit-transform-origin' : '0 0',
        'transform-origin'     : '0 0'
      });

      element.on('touchstart', touchstarthandler);
      element.on('touchmove', touchmovehandler);
      element.on('touchend', touchendhandler);
    };

    if (attrs.ngsrc) {
      image.src = attrs.ngsrc;
    } else {
      image.src = attrs.src;
    }

    /**
     * @param {object} evt
     */
    function touchstarthandler(evt) {
      var touches = evt.originalevent ? evt.originalevent.touches : evt.touches;

      startx = touches[0].clientx;
      starty = touches[0].clienty;
      initialpositionx = positionx;
      initialpositiony = positiony;
      movex = 0;
      movey = 0;
    }

    /**
     * @param {object} evt
     */
    function touchmovehandler(evt) {
      var touches = evt.originalevent ? evt.originalevent.touches : evt.touches;

      if (mode === '') {
        if (touches.length === 1 && scale > 1) {

          mode = 'swipe';

        } else if (touches.length === 2) {

          mode = 'pinch';

          initialscale = scale;
          initialdistance = getdistance(touches);
          originx = touches[0].clientx -
            parseint((touches[0].clientx - touches[1].clientx) / 2, 10) -
            element[0].offsetleft - initialpositionx;
          originy = touches[0].clienty -
            parseint((touches[0].clienty - touches[1].clienty) / 2, 10) -
            element[0].offsettop - initialpositiony;

        }
      }

      if (mode === 'swipe') {
        evt.preventdefault();

        movex = touches[0].clientx - startx;
        movey = touches[0].clienty - starty;

        positionx = initialpositionx + movex;
        positiony = initialpositiony + movey;

        transformelement();

      } else if (mode === 'pinch') {
        evt.preventdefault();

        distance = getdistance(touches);
        relativescale = distance / initialdistance;
        scale = relativescale * initialscale;

        positionx = originx * (1 - relativescale) + initialpositionx + movex;
        positiony = originy * (1 - relativescale) + initialpositiony + movey;

        transformelement();

      }
    }

    /**
     * @param {object} evt
     */
    function touchendhandler(evt) {
      var touches = evt.originalevent ? evt.originalevent.touches : evt.touches;

      if (mode === '' || touches.length > 0) {
        return;
      }

      if (scale < 1) {

        scale = 1;
        positionx = 0;
        positiony = 0;

      } else if (scale > maxscale) {

        scale = maxscale;
        relativescale = scale / initialscale;
        positionx = originx * (1 - relativescale) + initialpositionx + movex;
        positiony = originy * (1 - relativescale) + initialpositiony + movey;

      } else {

        if (positionx > 0) {
          positionx = 0;
        } else if (positionx < elwidth * (1 - scale)) {
          positionx = elwidth * (1 - scale);
        }
        if (positiony > 0) {
          positiony = 0;
        } else if (positiony < elheight * (1 - scale)) {
          positiony = elheight * (1 - scale);
        }

      }

      transformelement(0.1);
      mode = '';
    }

    /**
     * @param {array} touches
     * @return {number}
     */
    function getdistance(touches) {
      var d = math.sqrt(math.pow(touches[0].clientx - touches[1].clientx, 2) +
        math.pow(touches[0].clienty - touches[1].clienty, 2));
      return parseint(d, 10);
    }

    /**
     * @param {number} [duration]
     */
    function transformelement(duration) {
      var transition = duration ? 'all cubic-bezier(0,0,.5,1) ' + duration + 's' : '';
      var matrixarray = [scale, 0, 0, scale, positionx, positiony];
      var matrix   = 'matrix(' + matrixarray.join(',') + ')';

      element.css({
        '-webkit-transition' : transition,
        transition      : transition,
        '-webkit-transform' : matrix + ' translate3d(0,0,0)',
        transform      : matrix
      });
    }
  }

  return _directive;
};

上面代码中我们新建了一个directive，方便多个地方重用。

当我们建立好directive时候，该如何使用呢？

 <img style="width:100%;" src="assets/images/floorplan.jpeg" ng-pinch-zoom>

我们只需要在img文件上设定一个属性即可，是不是很简单呢？

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