Canvas保存图片到七牛云

摘要：最近在做一个项目，需要在前端对图片切片并上传到七牛云技术要点可将保存成二进制文件将二进制文件添加到中上传数据到后端处理代码实现目前没有看到七牛云提供的支持上传到云上的，所以这里自己实现了一下注意到七牛云的时候不要设置，让浏览器自己处理请求

最近在做一个项目，需要在前端对图片切片并上传到七牛云

canvas.toBlob(blob=>{}); //可将canvas保存成二进制文件

formData.append("file", blob, "filename"); //将二进制文件添加到FormData中

ajax.send(formData); //上传数据到后端处理

目前没有看到七牛云提供的JSSDK支持上传blob到云上的， 所以这里自己实现了一下
注意ajax post formData到七牛云的时候不要设置content-type，让浏览器自己处理

class Qiniu {
  constructor(options = {}) {
    this._options = {...options};
  }

  ajax(url = "", opt = {}) {
    const options = {method: "GET", async: true, dataType: "JSON", ...opt};
    return new Promise((resolve, reject) => {
      const ajax = this.createAjax();
      if (ajax) {
        const _async = typeof options.async === "boolean" ? options.async : true;
        ajax.open(options.method || "GET", url, _async);
        if (options.headers) {
          Object.keys(options.headers).forEach(key => {
            ajax.setRequestHeader(key, options.headers[key]);
          });
        }
        ajax.onreadystatechange = () => {
          if (ajax.readyState === 4) {
            if (ajax.status >= 200 && ajax.status <= 400) {
              let res = ajax.responseText;
              if (options.dataType && options.dataType.toUpperCase() === "JSON") {
                res = JSON.parse(res);
              }
              resolve(res, ajax.response);
            } else {
              reject(new Error("请求失败:" + ajax.status))
            }
          }
        };
        ajax.send(options.data);
      } else {
        reject(new Error("创建Ajax请求失败！"));
      }
    });
  }

  createAjax() {
    let xmlhttp;
    if (window.XMLHttpRequest) {
      xmlhttp = new XMLHttpRequest();
    } else {
      xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
    }
    return xmlhttp;
  }

  getToken() {
    if (this._options.token) {
      return Promise.resolve(this._options.token);
    } else {
      if (typeof this._options.getToken === "function") {
        const t = this._options.getToken();
        if (t && typeof  t.then === "function") {
          return t.then(token => {
            this._options.token = token;
            return token;
          })
        } else if (typeof t === "string") {
          this._options.token = t;
          return Promise.resolve(t);
        } else {
          return Promise.reject(new Error("options.getToken必须返回Promise或string token"));
        }
      } else if (typeof this._options.getTokenUrl === "string") {
        return this.ajax(this._options.getTokenUrl, {
          headers: {
            authorization: this._options.authorization
          }
        }).then(res => {
          this._options.token = res.uptoken;
          return this._options.token;
        }).catch(ex => {
          throw new Error("获取uptoken失败:" + ex.message);
        });
      } else {
        return Promise.reject(new Error("无法获取token"));
      }
    }
  }

  upload(file, filename, key) {
    return this.getToken().then(token => {
      const formData = new FormData();
      formData.append("key", key || filename);
      formData.append("token", token);
      formData.append("file", file, filename);
      return formData;
    }).then(data => {
            //注意不要设置content-type,浏览器自动会填充
      return this.ajax("http://upload.qiniu.com/", {
        method: "POST",
        data,
      });
    });
  }
}


canvas.toBlob(blob => {
    const filename = Date.now() + Math.random() + ".png";
    const qiniu = new Qiniu({getTokenUrl:"这里写获取七牛token的接口地址"});
    qiniu.upload(blob, filename);
}, "image/png");