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';


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;
    }

    
    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;
    }

    
    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();

      }
    }

    
    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 = '';
    }

    
    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);
    }

    
    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？

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？

如有疑问请留言或者到本站社区交流讨论，感谢阅读，希望能帮助到大家，谢谢大家对本站的支持！