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

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？

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！