h5移动端局部放大效果

首先添加zoom.js

(function (root, factory) {
if (typeof exports === 'object' && typeof module === 'object')
module.exports = factory();
else if (typeof define === 'function' && define.amd)
define([], factory);
else if (typeof exports === 'object')
exports["Zoom"] = factory();
else
root["Zoom"] = factory();
})(this, function () {

/**
* 简洁的元素缩放功能。
* @param {[type]} el 要缩放的元素
* @param {[type]} option {windth:元素宽度（必须），height:元素高度（必须），minScale:最小缩放比例，maxScale:最大缩放比例，top:原始位置,left:原始位置}
*/
function Zoom(el, option) {
if (!option || !option.width || !option.height) {
throw "dom的尺寸参数错误";
}
option = Object.assign({
minScale: 1,
maxScale: 3,
top: 0,
left: 0
}, option);

this.el = el;

this.lastSapce = 0;
this.touchState = 0;
this.lastPoint = null
this.targetPoint = null;

//放大缩小的倍数 当前缩放倍数
this.minScale = option.minScale || 1;
this.maxScale = option.maxScale || 10;

//dom的尺寸参数
this.width = option.width;
this.height = option.height;
this.top = option.top;
this.left = option.left;
this.scale = 1;

//初始位置 以及 初始宽高
this.originTop = option.top;
this.originLeft = option.left;
this.originW = this.width;
this.originH = this.height;
//图片中心点
this.centerX = this.left + this.originW / 2;
this.centerY = this.top + this.originH / 2;

this.el.style.position = 'absolute';

this.init();
return this;
}

Zoom.prototype.getTouches = function (event) {
let touches = event.touches;
if (!touches) {
touches = event.originalEvent.touches;
}
return touches;
}

Zoom.prototype.getTouchsDistance = function (t1, t2) {

let dx = parseInt(t1.pageX - t2.pageX);
let dy = parseInt(t1.pageY - t2.pageY);

let d = Math.pow((dx * dx + dy * dy), 0.5);

return d.toFixed(5);
}

Zoom.prototype.restView = function () {
this.el.style.width = this.width + 'px';
this.el.style.height = this.height + 'px';
this.el.style.top = this.top + 'px';
this.el.style.left = this.left + 'px';
}

Zoom.prototype.init = function () {

this.el.addEventListener('touchmove', this.touchmoveHandler);
this.el.addEventListener('touchstart', this.touchmoveHandler);
this.el.addEventListener('touchend', this.touchEndHandler);
this.el.addEventListener('touchcancel', this.touchEndHandler);
this.el.addEventListener('touchstart', this.dbclickHandler);
this.el.zoom = this;

}
Zoom.prototype.dbclickHandler = function (event) {
event.stopPropagation();
event.preventDefault();
let el = event.currentTarget;
let zoom = el.zoom;
let time = new Date(event.timeStamp).getTime();
let touchs = zoom.getTouches(event);
if (touchs.length == 1) {
if (!el.lastClickTime) {
el.lastClickTime = time;
} else {
if (time - el.lastClickTime < 300) {
el.lastClickTime = 0;
if (zoom.scale != 1) {
zoom.setScale(1);
} else if (zoom.scale == 1) {
zoom.setScale(2);
}
} else {
el.lastClickTime = time;
}
}
}
zoom.touchStartTime = new Date().getTime();
return false;
},
Zoom.prototype.drage = function (touch) {
if (this.lastPoint == null) {
this.lastPoint = {
x: touch.pageX,
y: touch.pageY,
}
} else {
let dx = parseInt(touch.pageX - this.lastPoint.x);
let dy = parseInt(touch.pageY - this.lastPoint.y);

this.lastPoint.x = touch.pageX;
this.lastPoint.y = touch.pageY;

this.left += dx;
this.top += dy;

this.setTransform(false);
}
}

Zoom.prototype.zoom = function (touchs) {

this.lastPoint = null;
let t1 = touchs[0];
let t2 = touchs[1];

let x1 = t1.pageX;
let x2 = t2.pageX;
let y1 = t1.pageY;
let y2 = t2.pageY;

let d = this.getTouchsDistance(t1, t2);

if (this.touchState == 0) {
this.lastSapce = d;
this.touchState = 1;

this.pointX = (x2 + (x1 - x2) / 2 - this.left) / this.scale;
this.pointY = (y2 + (y1 - y2) / 2 - this.top) / this.scale;

} else if (this.touchState == 1) {

let scaleChange = ((d / this.lastSapce) - 1) * 2;

let scale = this.scale + scaleChange / 2;

this.setScale(scale, this.pointX, this.pointY);

this.lastSapce = d;
}
}

Zoom.prototype.touchmoveHandler = function (event) {

event.stopPropagation();
event.preventDefault();
let el = event.currentTarget;
let zoom = el.zoom;
let touchs = zoom.getTouches(event);
if (touchs.length == 1) {
zoom.drage(touchs[0]);//拖动处理
} else if (touchs.length >= 2) {
zoom.lastPoint = null;//终止拖动事件
zoom.zoom(touchs);//缩放处理

}

return false;
}

Zoom.prototype.touchEndHandler = function (event) {
let zoom = event.currentTarget.zoom;

zoom.touchState = 0;
zoom.lastPoint = null;
zoom.lastSapce = 0;

let minSpace = 20;
let parentWidth = zoom.el.parentElement.offsetWidth;
let parentHight = zoom.el.parentElement.offsetHeight;
let scale = zoom.scale;

if (scale < zoom.minScale) {
scale = zoom.minScale;
}
if (scale > zoom.maxScale) {
scale = zoom.maxScale;
}

if (scale != zoom.scale) {
zoom.preSetScale(scale, zoom.lastPointX, zoom.lastPointY);
}

if ((zoom.left + zoom.width) < minSpace) {
zoom.left = - zoom.width + minSpace;
}
if (zoom.left >= (parentWidth - minSpace)) {
zoom.left = parentWidth - minSpace;
}

if ((zoom.top + zoom.height) < minSpace) {
zoom.top = - zoom.height + minSpace;
}
if (zoom.top >= (parentHight - minSpace)) {
zoom.top = parentHight - minSpace;
}

zoom.setTransform(true);

return;
}
Zoom.prototype.setTransform = function (needAnimation, originX, originY) {
let distanceX = this.left - this.originLeft;
let distanceY = this.top - this.originTop;
let scale = this.scale;
originX = originX == undefined ? (this.originTop + 'px') : originX;
originY = originY == undefined ? (this.originLeft + 'px') : originY;
this.el.style.transformOrigin = 'left top';
this.el.style.transform = 'matrix(' + scale + ',0,0,' + scale + ',' + distanceX + ',' + distanceY + ')';
if (needAnimation == true) {
this.el.style.transition = 'all .3s ease-in-out 0s'
} else {
this.el.style.transition = ''
}
}

Zoom.prototype.destroy = function () {

this.el.removeEventListener('touchmove', this.touchmoveHandler);
this.el.removeEventListener('touchstart', this.touchmoveHandler);
this.el.removeEventListener('touchend', this.touchEndHandler);
this.el.removeEventListener('touchcancel', this.touchEndHandler);

this.el.zoom = null;
}
//初始化放大倍数
Zoom.prototype.setScale = function (scale, pointX, pointY) {
this.preSetScale(scale, pointX, pointY);
this.setTransform(false);
}

Zoom.prototype.preSetScale = function (scale, pointX, pointY) {

if (scale < 0.1) {
scale = 0.1;
}

if (pointX == undefined) {
this.left = this.centerX - this.originW / 2 - this.originW / 2 * (scale - 1);
this.top = this.centerY - this.originH / 2 - this.originH / 2 * (scale - 1);

this.width = scale * this.originW;
this.height = scale * this.originH;

this.scale = scale;
} else {
this.width = scale * this.originW;
this.height = scale * this.originH;

this.left = this.left - pointX * (scale - this.scale);
this.top = this.top - pointY * (scale - this.scale);

this.lastPointX = pointX;
this.lastPointY = pointY;

this.scale = scale;
}

}

return Zoom;
});

下面是参考模板

<style>

#paper {
width: 100%;
height: 3100px;
overflow: hidden;
position: relative; /*重点*/
}

#detailBody {
position: absolute; /*重点*/
width: 100%;
height: 100%;
left: 0px;
top: 0px;
}

</style>

<script type="text/javascript">

$(function () {

var zoomEl = document.getElementById('detailBody');
var zoom = new Zoom(zoomEl, { 'top': 0, 'left': 0, 'width': $("#detailBody").width(), 'height': $("#detailBody").height() });
zoom.setScale(1);

});

</script>

<div id="paper" style="margin-top: 30px;">
<div class="layui-card-body" style="padding: 10px;" id="detailBody">

</div>
</div>