https://developers.weixin.qq.com/miniprogram/dev/api/media/image/wx.chooseImage.html

代码片段

shareInst.wx.chooseImage({
  count: 1, // 默认9
  sourceType: ['camera'],
  success: function (resp) {
    console.log("小程序", resp)
    shareInst.wx.checkJsApi({
      jsApiList: shareData.jsApiList,
      success: function (jsApiRes) {
        if (jsApiRes.checkResult.getLocalImgData) {
          shareInst.wx.getLocalImgData({
            localId: resp[0], // 图片的localID
            success: function (res) {
              var localData = res.localData; // localData是图片的base64数据，可以用img标签显示
              if (localData.indexOf(";base64,") == -1) {//兼容处理，安卓获取的图片base64码没有前缀，而苹果有,base64前缀并不固定
                localData = "data:image/jpeg;base64," + localData;//加上base64前缀
              }
              if (localData.indexOf("data:image/jgp;base64,") != -1) {//兼容处理，若是苹果手机，将前缀中的jgp替换成jpeg
                localData = localData.replace("data:image/jgp;base64,", "data:image/jpeg;base64,");
              }
              _this.nimSendFileByUrl(localData);
            }
          });
        } else {
          if (resp.length) {
            shareInst.app.$vux.loading.show({text: `正在发送...`});
          }
          console.log("resp[0]", resp);
          let {localIds} = resp
          console.log("resp[0]", localIds);
          shareInst.wx.uploadImage({
            localId: localIds[0], // 需要上传的图片的本地ID，由chooseImage接口获得
            isShowProgressTips: 1, // 默认为1，显示进度提示
            success: function (res) {
              console.log("成功", res);
              var serverId = res.serverId; // 返回图片的服务器端ID
              let params = {wxCode: shareData.launchParams.wxCode, mediaId: serverId};
              console.log("上传图片的id", params);
              shareInst.Api.getMedia(params).then(mediaResp => {
                if (mediaResp.code == 0 && mediaResp.result.length > 0) {
                  _this.nimSendFileByUrl(mediaResp.result);
                } else {
                  shareInst.app.$vux.loading.hide();
                }
              });
            },
            fail: function (error) {
              console.log("fail", error);
              shareInst.app.$vux.loading.hide();
            },
            cancel: function (error) {
              console.log("cancel", error);
              shareInst.app.$vux.loading.hide();
            }
          });
        }
      }
    });
  },
  fail: function (res) {

  }
})