上传视频并截图，跨域报错的解决办法

跨域报错的原因

最开始上传视频成功后，video标签的src会直接引入上传后的服务端资源地址，然后使用canvas截图就发生了跨域报错的提示。

failed to execute 'todataurl' on 'htmlcanvaselement': tainted canvases may not be exported.

按网上说的方法设置video标签的属性 crossorigin="anonymous",还是报错，原因是服务端的请求头没设置，不允许跨域访问。

failed to load http://xxxx.oss-cn-shenzhen.aliyuncs.com/2018/08/22/1749/vu0sl0mssljvn1q3ynn2fmr1e4zmme0vmhtv7a9s.mp4: no 'access-control-allow-origin' header is present on the requested resource. origin 'http://localhost:8080' is therefore not allowed access.

解决办法： 视频上传成功后，不要引入线上地址，仍然使用本地视频地址，即可解决跨域问。

完整代码

<template>
  <div>
    <video ref='videoview' crossorigin="anonymous" v-show="videoid" :src="videopath" controls="controls" class="video-upload-post-preview m-box-center m-box-center-a image-wrap more-image img3"></video>
    <input ref='videofile' id="selectvideo" type="file" name="file" @change="uploadvideo" class="upload__input m-rfile">
  </div>
</template>

<script>
  import sendimage from "@/util/sendimage.js";
  export default {
    data() {
      return {
        videoid: "",
        videopath: "",
        videocover: ""
      }
    },
    methods: {
      uploadvideo(e) {
        let file = e.target.files[0];
        sendimage(file)
          .then(id => {
            // console.log(id)
            this.videoid = id
            this.videopath = url.createobjecturl(file)
            settimeout(() => {
              this.captureimage(file);
            }, 300);
          })
          .catch(e => {
            this.$message.error("上传失败，请稍后再试");
          });
      },
      captureimage(file) {
        let video = this.$refs.videoview;
        // console.log(this.$refs, video)
        var canvas = document.createelement("canvas"); //创建一个canvas 
        canvas.width = video.videowidth * 0.8; //设置canvas的宽度为视频的宽度 
        canvas.height = video.videoheight * 0.8; //设置canvas的高度为视频的高度 
        canvas.getcontext('2d').drawimage(video, 0, 0, canvas.width, canvas.height); //绘制图像 
        let imgbase64 = canvas.todataurl()
        let imgfile = this.datatofile(imgbase64)
        // console.log('img', imgfile)
        sendimage(imgfile)
          .then(id => {
            this.videocover = id
          })
          .catch(e => {
            this.$message.error("上传失败，请稍后再试");
          });
      },
      datatofile(urldata) {
        var bytes = window.atob(urldata.split(',')[1]); //去掉url的头，并转换为byte  
        //处理异常,将ascii码小于0的转换为大于0  
        var ab = new arraybuffer(bytes.length);
        var ia = new uint8array(ab);
        for (var i = 0; i < bytes.length; i++) {
          ia[i] = bytes.charcodeat(i);
        }
        return new blob([ab], {
          type: 'image/jpg'
        });
      }
    }
  }
</script>