<input id="takepicture" type="file" accept="image/*" capture="camera" style="display: none">

var takePictureOnclick = function(){var takePicture = document.getElementById('takepicture');... // 添加需要处理的代码takePicture.click();
}

 1 // 监听照片拍摄,并获取照片流
 2 var takePicture = document.getElementById('takepicture');
 3 var takePictureUrl = function () {
 4     takePicture.onchange = function (event) {
 5         var files = event.target.files, file;
 6         if (files && files.length > 0) {
 7             file = files[0];
 8             try {
 9                 var URL = window.URL || window.webkitURL;
10                 var blob = URL.createObjectURL(file);　　// 获取照片的文件流
11                 compressPicture(blob);　　// 压缩照片
12             }
13             catch (e) {
14                 try {
15                     var fileReader = new FileReader();
16                     fileReader.onload = function (event) {　　　　// 获取照片的base64编码
17                         compressPicture(event.target.result);　　// 压缩照片
18                     };
19                     fileReader.readAsDataURL(file);
20                 }
21                 catch (e) {
22                     alert(common.MESSAGE.title.error, '拍照失败,请联系客服或尝试更换手机再试!');
23                 }
24             }
25         }26     }
27 }();

 1 var compressPicture = function (blob) {
 2   var quality = 0.5, image = new Image();
 3   image.src = blob;
 4   image.onload = function () {
 5     var that = this;
 6     // 生成比例
 7     var width = that.width, height = that.height;
 8     width = width / 4;
 9     height = height / 4;
10     // 生成canvas画板
11     var canvas = document.createElement('canvas');
12     var ctx = canvas.getContext('2d');
13     canvas.width = width;
14     canvas.height = height;
15     ctx.drawImage(that, 0, 0, width, height);
16     // 生成base64,兼容修复移动设备需要引入mobileBUGFix.js
17     var imgurl = canvas.toDataURL('image/jpeg', quality);
18     // 修复IOS兼容问题
19     if (navigator.userAgent.match(/iphone/i)) {
20       var mpImg = new MegaPixImage(image);
21       mpImg.render(canvas, {
22         maxWidth: width,
23         maxHeight: height,
24         quality: quality
25       });
26       imgurl = canvas.toDataURL('image/jpeg', quality);
27     }
28     // 上传照片
29     uploadPicture(imgurl);
30   };
31 };