基于HTML5+JS实现本地图片裁剪并上传功能

最近做了一个项目，这个项目中需要实现的一个功能是：用户自定义头像（用户在本地选择一张图片，在本地将图片裁剪成满足系统要求尺寸的大小）。这个功能的需求是：头像最初剪切为一个正方形。如果选择的图片小于规定的头像要求尺寸，那么这整张图片都会作为头像。如果大于规定的尺寸，那么用户可以选择要裁剪的区域。用户点击确定按钮，就将裁剪得到的图片数据发送到服务器，在后端将图片数据保存成一个文件。

要完成上述功能，涉及到的知识有：ajax，canvas和html5中的files接口。我将实现这个功能的代码封装到了4个模块中，分别是ajax.js，preview.js，shear.js和customerImg.js。

ajax.js:用于发送ajax请求。

preview.js:用于图片预览

shear.js：用于裁剪图片

customer.js:自定义头像。在这个模块中药引入ajax.js，preview.js和shear.js

我使用webpack进行打包。我还使用了jquery和jquery-ui。

我从这个项目中抽离出了这个功能。下面是这个功能的详细代码。

1.HTML代码

  
   
   选择图片
  
  
   
    
     
     
    
   

   
    
预览
    
    

     确定
    
   
  
 

2.CSS代码

.clearfix:after{
 content: "";
 display: block;
 clear: both;
 height: 0;
 overflow: hidden;
 visibility: hidden;
}
img{
　　vertical-align: middle;
　　max-width:100%
}
.m-warp{
 width: 800px;
}
.item{
 margin-top: 20px;
}
.col{
 float: left;
}
.col-1{
 position: relative;
 width: 450px;
 height: 450px;
 outline: 1px solid #333;
}
.preview{
 display: inline-block;
}
.col-2{
 width: 300px;
 margin-left: 50px;
}
label{
 display: block;
 text-align: center;
 width: 100px;
 font-size: 16px;
 color: #fff;
 background-color: #888888;
 height: 30px;
 line-height: 30px;
}
.mask{
 position: absolute;
 z-index: 1;
 top:0;
 left: 0;
 bottom: 0;
 right: 0;
 background-color: rgba(0,0,0,.4);
}
.cvsMove{
 position: absolute;
 z-index: 2;
 outline: 2px dotted #333;
 cursor: move;
 display: none;
}

有了css和html的运行结果如下：

3.js代码

customerImg.js

var $ = require('jquery');
var ajax = require('./ajax.js');
var preview = require('./preview.js');
var shear = require('./shear.js');

function CustomerImg() {
 this.isSupport = null;
 this.previewBox = null;
 this.warp = null;
}

CustomerImg.prototype.start = function (warp) {
 var info,me,warpBox;
 me = this;
 this.isSupport = this.__isSupport();
 if(!this.isSupport) {
  info = $('
你的浏览器不支持自定义头像，可更换高版本的浏览器自定义头像
');
  $('body').html(info);
  return this;
 }
 //判断操作区域示范存在
 if(warp && warp.length > 0){
  this.warp = warp;
 }else{
  return this;
 }
 //预览
 preview.start(warp,shear.start.bind(shear,warp));
 this.previewBox = warp.find('#preview');
 //确定
 warp
  .find('#submit')
  .unbind('click')
  .on('click',me.__submit.bind(me));
};

CustomerImg.prototype.__submit = function () {
 var cvsMove,data,fd;
 cvsMove = this.previewBox.find('#cvsMove');
 data = cvsMove[0].toDataURL('image/jpg',1);
 fd = {
  'customerImg':data
 };
 ajax.upload(fd);
};

CustomerImg.prototype.__isSupport = function () {
 var canvas,context;
 canvas= document.createElement('canvas');
 if(typeof FileReader === 'function'&& canvas.getContext && canvas.toDataURL){
  return true;
 }else{
  return false;
 }
};
var customerImg = new CustomerImg();
module.exports = customerImg;

preview.js

var $ = require('jquery');

function Preview() {
 this.boxElem = null;
 this.callback = null;
 this.type = null;
}

Preview.prototype.start = function (boxElem,callback) {
 var chooseFile,me;
 me = this;
 if(! boxElem || boxElem.length <= 0) return this;
 this.boxElem = boxElem;
 if(typeof callback === 'function'){
  this.callback = callback;
 }
 if(this.__isSupport()){
  chooseFile = boxElem.find('input[type="file"]');
  chooseFile
   .on('change',me.fileChange.bind(me))
 }
};

Preview.prototype.fileChange = function (event) {
 var target,reader,file,me,type;
 target = event.target;
 me = this;
 file = target.files[0];
 type = file.type;
 this.type = type;
 if(type !== 'image/png' && type !== 'image/jpg' && type !== 'image/jpeg'){
  alert('文件格式不正确');
  return this;
 }
 reader = new FileReader();
 if(file){
  reader.readAsDataURL(file);
 }
 reader.onload = function () {
  me.show(reader);
 }
};

Preview.prototype.show = function (reader) {
 var preView,img,me;
 preView = this.boxElem.find('#preview');
 img = preView.find('#preImg');
 me = this;
 if(img.length <= 0){
  preView.append($(''));
 }
 img = preView.find('#preImg');
 //确保图片加载完成后再执行回调
 img.on('load',function () {
  if(me.callback){
   me.callback(me.type);
  }
 });
 img.attr('src',reader.result);
};

Preview.prototype.__isSupport = function () {
 return typeof FileReader === 'function';
};
var preview = new Preview();
module.exports = preview;

shear.js

var $ = require('jquery');
//由于要使用jquery-ui，所以将$暴露到window上。
window.$ = $;
require('./jquery-ui.min.js');

function Shear() {
 this.previewBox = null;
 this.cvsMove = null;
 this.maxW = 200;
 this.maxH = 200;
 this.thum = null;
 this.fileType = 'image/jpeg';
}

Shear.prototype.start = function (previewBox,fileType) {
 if(!arguments.length) return this;
 var me = this;
 this.previewBox = previewBox;
 if(fileType){
  this.fileType = fileType;
 }
 this.thum = this.previewBox.find('#thum');
 this.cvsMove = this.previewBox.find('#cvsMove');
 this.showCanvas();
 return this;

};

Shear.prototype.showCanvas = function () {
 var preImg,h,w,me,cvsH,cvsW,rateH,rateW,naturalH,naturalW,preview;
 me = this;
 preImg = this.previewBox.find('#preImg');
 preview = this.previewBox.find('#preview');
 naturalH = preImg[0].naturalHeight;
 naturalW = preImg[0].naturalWidth;
 //将canvas显示出来
 this.cvsMove.show();
 //将canvas置于（0,0）
 this.cvsMove
  .css({
   "left":'0',
   'top':'0'
  });
 h = preImg.height();
 w = preImg.width();
 //规定裁剪出的图片尺寸为200px*200px
 //要保证裁剪的图片不变形
 if(h < this.maxH || w < this.maxW){
  this.cvsMove[0].width = cvsW = Math.min(h,w);
  this.cvsMove[0].height = cvsH = Math.min(h,w);
 }else{
  this.cvsMove[0].width= cvsW = this.maxW;
  this.cvsMove[0].height= cvsH = this.maxH;
 }
 rateH = h/naturalH;
 rateW = w/naturalW;
 this.__drawImg(preImg,0,0,cvsW/rateW,cvsH/rateH,0,0,cvsW,cvsH);
 //使用jquery-ui中的功能使canvas可以移动
 this.cvsMove.draggable(
  {
   containment: "parent",
   drag:function (event,ui) {
    var left,top;
    left = ui.position.left;
    top = ui.position.top;
    //canvas每次移动都有从新绘制图案
    me.__drawImg(preImg,left/rateW,top/rateH,cvsW/rateW,cvsH/rateH,0,0,cvsW,cvsH);
   }
  }
 )
};

Shear.prototype.__drawImg = function (myImg,sx,sy,sW,sH,dx,dy,dW,dH) {
 var cxt,thum,me;
 me = this;
 cxt = this.cvsMove[0].getContext('2d');
 cxt.drawImage(myImg[0],sx,sy,sW,sH,dx,dy,dW,dH);
 thum = this.thum;
 //将canvas上的图案显示到右侧
 thum
  .attr('src',this.cvsMove[0].toDataURL(me.fileType,1))
  .width(this.maxW)
  .height(this.maxH)
};
var shear = new Shear();
module.exports = shear;

ajax.js

var $ = require('jquery');
function Ajax() {

}

Ajax.prototype.upload = function (data) {
 $.ajax({
  type:'POST',
  data:data,
  dataType:'json',
  url:'/test/PHP/upload.php',
  success:function (result) {
   if(result.status){
    location.reload();
   }else{
    alert(result.msg);
   }
  }
 });
};
var ajax = new Ajax();
module.exports = ajax;

最后在另一个文件中，调用customerImg对象的start方法

var $ = require('jquery');
var customerImg =require('./customerImg.js');
customerImg.start($('#warp'));

webpack的配置文件如下：

var webpack = require('webpack');
module.exports = {
 entry:{
  'customerImg':'./js/test.js',
  'jQuery':['jquery']
 },
 output:{
  filename:'[name].js',
  library:'jQuery',
  libraryTarget:'umd'
 },
 plugins:[
  new webpack.optimize.CommonsChunkPlugin({
   name:'jQuery',
   filename:'jquery.js'
  })
 ]
};

 效果：

4.php代码

if(!empty($_POST) && isset($_POST['customerImg'])){
 $img = $_POST['customerImg'];
 $imgdata = explode(',', $img);
 $uniName = md5 ( uniqid ( microtime ( true ), true ) );
 $a = file_put_contents('./../uploads/'.$uniName.'.jpg', base64_decode($imgdata[1]));
}

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