一、保存图片

   微信小程序中使用得比较多的就是分享功能，基本上都会用到，尤其是对二维码图片，保存在本地或者将小程序分享给朋友，好在微信小程序提供的api中已经告诉了该怎么使用，下面就将所用到的分享出来。
   首先是通过请求后端接口获取图片地址，当然也可以不用请求直接将地址写死。

 wx.request({        url: getApp().data.serviceUrl +'/wechat/searchdata/proqrcode',//请求地址        data: {//发送给后台的数据          openid: that.data.openid        },        header: {//请求头          "Content-Type": "application/json;charset=UTF-8;"        },        method: "POST",//get为默认方法/POST        success: function (res) {          var imageurl = res.data.content          that.setData({            shareImgSrc: getApp().data.qrServiceUrl + imageurl          })          wx.getImageInfo({            src: that.data.shareImgSrc,//服务器返回的带参数的小程序码地址            success: function (res) {              //res.path是网络图片的本地地址              var qrCodePath = res.path;              //2. canvas绘制文字和图片              const ctx = wx.createCanvasContext('myCanvas');              // var imgPath = that.data.localImageUrl;              ctx.drawImage(qrCodePath, 0, 0, 200, 200);              ctx.setFillStyle('white')              ctx.fillRect(0, 520, 600, 280);              ctx.draw()              // that.setData({              //   localImageUrl: qrCodePath              // })            },            fail: function (res) {              //失败回调            }          });        },        fail: function (err) { },//请求失败      })

   经过上面一步已经图片展示出来了，接下来是将图片保存下来。这里通过按钮点击实现：

savedate: function (e) {      var that = this;      wx.canvasToTempFilePath({        x: 0,        y: 0,        width: 200,        height: 200,        destWidth: 400,        destHeight: 400,        canvasId: 'myCanvas',        success: function (res) {          that.setData({            saveImgSrc: res.tempFilePath          })        },        fail: function (res) {          console.log(res)        }      })         //4. 将图片保存到相册        wx.saveImageToPhotosAlbum({          filePath: that.data.saveImgSrc,          success(res) {            wx.showModal({              title: '存图成功',              content: '图片成功保存到相册了，去发圈噻~',              showCancel: false,              confirmText: '好哒',              confirmColor: '#72B9C3',              success: function (res) {                if (res.confirm) {                  console.log('用户点击确定');                }                // that.hideShareImg()              }            })          }        })    },

二、分享小程序

   分享小程序需要在button中设置open-type，如下

<button class='sendfriend' bindtap = 'sendfriend' open-type="share">发送给微信好友</button>

   通过onShareAppMessage方法实现发送给好友：

onShareAppMessage: function (ops) {      if (ops.from === 'button') {        // 来自页面内转发按钮        console.log(ops.target)      }      var that = this      return {        title: '分享给好友',         path: 'pages/index/index?scene='+that.data.openid,//点击分享消息是打开的页面        imageUrl: that.data.saveImgSrc,        success: function (res) {          // 转发成功          console.log("转发成功:" + JSON.stringify(res));          var shareTickets = res.shareTickets;        },        fail: function (res) {          // 转发失败          console.log("转发失败:" + JSON.stringify(res));        }      }    },