js照相并修图

<div class="photobooth">
     <div class="controls">
        <!--绑定点击拍照函数takePhoto()-->
       <button onClick="takePhoto()">Take Photo</button>
         <!--绑定点击保存照片函数savePhoto()-->
       <button onClick="savePhoto()">Save Photo</button>
     <div class="rgb">
         <!--六种颜色，不同移动位置，RGB值不同-->
         <label for="rmin">Red Min:</label>
         <input type="range" min=0 max=255 name="rmin" value="0">
         <label for="rmax">Red Max:</label>
         <input type="range" min=0 max=255 name="rmax" value="255">
         <br>
         <label for="gmin">Green Min:</label>
         <input type="range" min=0 max=255 name="gmin" value="0">
         <label for="gmax">Green Max:</label>
         <input type="range" min=0 max=255 name="gmax" value="255">
         <br>
         <label for="bmin">Blue Min:</label>
         <input type="range" min=0 max=255 name="bmin" value="0">
         <label for="bmax">Blue Max:</label>
         <input type="range" min=0 max=255 name="bmax" value="255">
       </div> 
     </div>
     <div class="hasimg">
     <p>照片区域：</p>
     <canvas class="photo" height="400" width="500"></canvas>
     </div>
     <div class="hasimg">
     <p>实时视频区域：</p>
     <video class="player"></video>
     </div>
     <div class="hasimg">
     <p>变色画布区域:</p>
     <div class="strip">
     <a href="">
       <img alt="暂未保存图像" id='myimg'>
     </a>
     </div>
     </div>
   </div>
   <audio class="snap" src="2.mp3" ></audio>

function askWebcam() {
     //用于向设备申请照相功能
     navigator.getUserMedia = navigator.getUserMedia ||
         navigator.webkitGetUserMedia ||
         navigator.mozGetUserMedia;
     if (navigator.getUserMedia) {
         navigator.getUserMedia({
             audio: false,
             video: {
                 width: 300,
                 height: 200
             }
         }, function(stream) {
             //若成功
             video.srcObject = stream;
             video.onloadedmetadata = function(e) {
                 video.play();
             }
         }, function(err) {
             console.log('Error occured:' + err.name);
         });
     } else {
         console.log('this navigator doesn\'t support webcam!');
     }
 }

//点击函数
 function takePhoto() {
     ctx.drawImage(video, 0, 0, 300, 200);
     //将原始截图保存
     origindata = ctx.getImageData(0, 0, 300, 200);
     //点击拍照图片时播放音乐
     audio.play()
 }
 ​
 //保存图片
 function savePhoto() {
     img.src = canvas.toDataURL();
     a.href = canvas.toDataURL();
     a.setAttribute('download', 'handsome');
 }

slider.onchange = function changeImage(e) {
     //先将canvas恢复至原始截图
         ctx.putImageData(origindata, 0, 0);
         const target = e.target;
  //startPos表示操作像素点数据时的起点，
 //从canvas获取到的像素数据每四个值表示一个像素点
    //例如滑块为红色，则只需要改变像素数组中第0,4,8......个元素的值。
         const startPos = {
             'r': 0,
             'g': 1,
             'b': 2
         }[target.name[0]];
         //filterMin和filterMax表示相应的滤色范围上下限，
       //若修改了红色滤色范围则取红色范围值。
         //若修改蓝色的滤色范围，则取蓝色。
         var tempFilter = checkFilter(target.name, target.value);
         const filterMin = tempFilter.min;
         const filterMax = tempFilter.max;
         //从canvas获取像素数据
         var img = ctx.getImageData(0, 0, 300, 200);
 ​
         var imgd = img.data;
         //色彩过滤
         for (var i = startPos, len = imgd.length; i < len; i += 4) {
             if (imgd[i] < filterMin) {
                 imgd[i] = filterMin;
             } else if (imgd[i] > filterMax) {
                 imgd[i] = filterMax;
             }
         }
         //将修改后的像素数据重绘制至canvas
         ctx.putImageData(img, 0, 0);
         img.src = canvas.toDataURL();
     }
 }

function checkFilter(name, value) {
     var _min;
     var _max;
     var _antiname = {
         'rmin': 'rmax',
         'rmax': 'rmin',
         'gmin': 'gmax',
         'gmax': 'gmin',
         'bmin': 'bmax',
         'bmax': 'bmin'
     }[name]
     filter[name] = value;
     //当下限值超过上限时，将两者对调
     _min = Math.min(filter[name], filter[_antiname]);
     _max = Math.max(filter[name], filter[_antiname]);
     console.log(filter);
     return {
         min: _min,
         max: _max
     }
 }

window.onload = function() {
     canvas = document.querySelector('canvas');
     video = document.querySelector('video');
    audio=document.querySelector('audio')
     ctx = canvas.getContext('2d');
     img = document.querySelector('#myimg');
     slider = document.querySelector('.rgb');
     a = document.querySelector('a');
     //滤色范围记录
     filter = {
         rmin: 0,
         rmax: 255,
         gmin: 0,
         gmax: 255,
         bmin: 0,
         bmax: 255
     }
     //调用摄像头数据
       askWebcam();
       changeImage(e)
  }
  //点击函数
  takePhoto()
  //保存图片
  savePhoto()
 //申请网络摄像头操作权限
  askWebcam() 
 //滤色函数
  checkFilter(name, value) 

 html,body{
     padding: 0;
     margin: 0;
     height: 100%;
     width: 100%;
 }
 .player{
     height:200px;
     width:300px;
 }
 .hasimg{
     display:inline-block;
     vertical-align: top;
 }
 .strip{
     height:200px;
     width:300px;
 }
 .controls{
     margin-left:400px;
     background-color: aqua;
     width:600px;
     height:200px;
 }
 .controls button{
     margin:10px 50px;
 ​
 }
 .rgb{
     margin-top:50px;
     text-align: center;
 }