AngularJS1.x学习（仿微信图片手势缩放效果实现）

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？

最后

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