vue头像上传与文件压缩

工作中遇到的问题记录：vue开发头像上传组件，后端提供接口，需求为可相册上传，可相机拍摄上传，文件大小限制为2M

需求点分析

1. 移动端调用相册/摄像头实现拍照
2. 图片压缩，当前高像素的相机拍出来的图片都有个4-5m大小，超出了限定的2m
3. 图片上传

第一点：移动端调用相册/摄像头实现拍照

这就比较简单了，H5的标签足已经能满足我们的要求了，我们要做的只是让它更美观一点

        <div class="yb-headSet-but">
          <div class="btn-box">
            <input type="file" accept="image/*" @change="uploadImg" class="fromAlbum">   //设置input opacity为0，定位覆盖a标签，a标签设置为设计稿的按钮样式
            <a href="" class="weui-but">从相册选一张</a>
          </div>
          <div class="btn-box">
            <a href="" class="weui-but">拍一张照片</a>
            <input type="file" accept="image/*" @change="uploadImg" capture="camera" class="fromCamera">    //两者区别：capture="camera" 可直接调用摄像头
          </div>
        </div>         

第二点：图片压缩

利用的是canvas的drawImage 和 toDataURL的api，具体代码是复制的 https://www.jianshu.com/p/4587312d2f44
修改了几个大佬笔误的地方

imgResize(file, callback) {
      var _this = this;
      var fileReader = new FileReader();
      fileReader.onload = function() {
        var IMG = new Image();
        IMG.src = this.result;
        IMG.onload = function() {
          var w = this.naturalWidth,
            h = this.naturalHeight,
            resizeW = 0,
            resizeH = 0;
          // maxSize 是压缩的设置，设置图片的最大宽度和最大高度，等比缩放，level是报错的质量，数值越小质量越低
          var maxSize = {
            width: 500,
            height: 500,
            level: 0.6
          };
          if (w > maxSize.width || h > maxSize.height) {
            var multiple = Math.max(w / maxSize.width, h / maxSize.height);
            resizeW = w / multiple;
            resizeH = h / multiple;
          } else {
            // 如果图片尺寸小于最大限制，则不压缩直接上传
            return callback(file);
          }
          var canvas = document.createElement("canvas");
          var ctx = canvas.getContext("2d");
          if (window.navigator.userAgent.indexOf("iPhone") > 0) {
            canvas.width = resizeH;
            canvas.height = resizeW;
            ctx.rotate(90 * Math.PI / 180);
            ctx.drawImage(IMG, 0, -resizeH, resizeW, resizeH);
          } else {
            canvas.width = resizeW;
            canvas.height = resizeH;
            ctx.drawImage(IMG, 0, 0, resizeW, resizeH);
          }
          var base64 = canvas.toDataURL("image/" + _this.fileType, maxSize.level);
          _this.convertBlob(window.atob(base64.split(",")[1]), callback);
        };
      };
      fileReader.readAsDataURL(file);
    },

图片上传

使用canvas.toDataURL获得的是base64格式，上传时需要转换成Blob二进制格式，使用formData提交

//Blob对象生成
convertBlob(base64, callback) {
      var buffer = new ArrayBuffer(base64.length);
      var ubuffer = new Uint8Array(buffer);
      for (var i = 0; i < base64.length; i++) {
        ubuffer[i] = base64.charCodeAt(i);
      }
      var blob;
      try {
        blob = new Blob([buffer], { type: "image/" + this.fileType });
      } catch (e) {
        window.BlobBuilder =
          window.BlobBuilder ||
          window.WebKitBlobBuilder ||
          window.MozBlobBuilder ||
          window.MSBlobBuilder;
        if (e.name === "TypeError" && window.BlobBuilder) {
          var blobBuilder = new BlobBuilder();
          blobBuilder.append(buffer);
          blob = blobBuilder.getBlob("image/" + this.fileType);
        }
      }
      callback(blob);
    },
//提交函数
postImg(file) {
      let image = new FormData();
      image.append("file", file, this.random_string(12) + '.' + this.fileType);
      console.log(image);
      setHead(image).then(res => {
        this.$indicator.close();
        if (res.Success) {
          let newPath = res.photoPath +'?t=' + this.random_string(12);
          this.$store.commit("UPDATE_BASEINFO", { photoPath: newPath });
          this.picValue = newPath;
          this.$messagebox.alert(res.Message);
        } else {
          this.$messagebox.alert(res.Message);
        }
      });
    },

注意注意 这里有个巨大的坑。。。。。

这个坑是这样的，我使用压缩过的Blob格式提交后台时，返回提示文件格式不正确，不属于jpeg、jpg等，这我就纳闷了，我上传的formData里面写明了文件格式了啊；
后来经过简书大佬 一斤代码 老大的帮助，老大测试后说出了问题所在：那就是 FormData.append('file', file),如果只有两个参数，（第三个参数是文件名）的情况下，默认fileName=“blob”，这样上次至后台，如果后台未做其他处理的话，就会出现报错的情况，后来就添加了随机文件名，完整代码如下

<template>
  <div class="yb-page">
    <div class="yb-page-inner">
      <div class="yb-headSetting">
        <div class="yb-headSet-img">
          <img :src="picValue" alt="" onerror="this.src='https://ixxxxxx.com/we/tmpls/t9000/img/account/blackHead@2x.png'">
        </div>
        <div class="yb-headSet-but">
          <div class="btn-box">
            <input type="file" ref="avatarInput" accept="image/*" @change="uploadImg" class="fromAlbum">
            <a href="" class="weui-but">从相册选一张</a>
          </div>
          <div class="btn-box">
            <a href="" class="weui-but">拍一张照片</a>
            <input type="file" accept="image/*" @change="uploadImg" capture="camera" class="fromCamera">
          </div>
        </div>
      </div>
    </div>
  </div>
</template>
<script>
import { setHead } from "@/api/user";
export default {
  data() {
    return {
      picValue: this.$store.getters.baseInfo.photoPath,
      file: null,
      fileType: ''
    };
  },
  methods: {
    uploadImg(e) {
      if (e.target.value == "") {
        return;
      }
      this.$indicator.open();
      let files = e.target.files || e.dataTransfer.files;
      if (!files.length) return;
      this.file = files[0];
      this.fileType = this.file.type.split('/')[1];
      this.imgResize(files[0], this.postImg);
    },
    postImg(file) {
      let image = new FormData();
      image.append("file", file, this.random_string(12) + '.' + this.fileType);
      console.log(image);
      setHead(image).then(res => {
        this.$indicator.close();
        if (res.Success) {
          let newPath = res.photoPath +'?t=' + this.random_string(12);
          this.$store.commit("UPDATE_BASEINFO", { photoPath: newPath });
          this.picValue = newPath;
          this.$messagebox.alert(res.Message);
        } else {
          this.$messagebox.alert(res.Message);
        }
      });
    },
    imgResize(file, callback) {
      var _this = this;
      var fileReader = new FileReader();
      fileReader.onload = function() {
        var IMG = new Image();
        IMG.src = this.result;
        IMG.onload = function() {
          var w = this.naturalWidth,
            h = this.naturalHeight,
            resizeW = 0,
            resizeH = 0;
          // maxSize 是压缩的设置，设置图片的最大宽度和最大高度，等比缩放，level是报错的质量，数值越小质量越低
          var maxSize = {
            width: 500,
            height: 500,
            level: 0.6
          };
          if (w > maxSize.width || h > maxSize.height) {
            var multiple = Math.max(w / maxSize.width, h / maxSize.height);
            resizeW = w / multiple;
            resizeH = h / multiple;
          } else {
            // 如果图片尺寸小于最大限制，则不压缩直接上传
            return callback(file);
          }
          var canvas = document.createElement("canvas");
          var ctx = canvas.getContext("2d");
          if (window.navigator.userAgent.indexOf("iPhone") > 0) {
            canvas.width = resizeH;
            canvas.height = resizeW;
            ctx.rotate(90 * Math.PI / 180);
            ctx.drawImage(IMG, 0, -resizeH, resizeW, resizeH);
          } else {
            canvas.width = resizeW;
            canvas.height = resizeH;
            ctx.drawImage(IMG, 0, 0, resizeW, resizeH);
          }
          var base64 = canvas.toDataURL("image/" + _this.fileType, maxSize.level);
          _this.convertBlob(window.atob(base64.split(",")[1]), callback);
        };
      };
      fileReader.readAsDataURL(file);
    },
    convertBlob(base64, callback) {
      var buffer = new ArrayBuffer(base64.length);
      var ubuffer = new Uint8Array(buffer);
      for (var i = 0; i < base64.length; i++) {
        ubuffer[i] = base64.charCodeAt(i);
      }
      var blob;
      try {
        blob = new Blob([buffer], { type: "image/" + this.fileType });
      } catch (e) {
        window.BlobBuilder =
          window.BlobBuilder ||
          window.WebKitBlobBuilder ||
          window.MozBlobBuilder ||
          window.MSBlobBuilder;
        if (e.name === "TypeError" && window.BlobBuilder) {
          var blobBuilder = new BlobBuilder();
          blobBuilder.append(buffer);
          blob = blobBuilder.getBlob("image/" + this.fileType);
        }
      }
      callback(blob);
    },
    random_string(len) {
      len = len || 32;
      var chars = "ABCDEFGHJKMNPQRSTWXYZabcdefhijkmnprstwxyz2345678";
      var maxPos = chars.length;
      var pwd = "";
      for (var i = 0; i < len; i++) {
        pwd += chars.charAt(Math.floor(Math.random() * maxPos));
      }
      return pwd;
    }
  }
};
</script>