现在老板一般都需要线上推广功能，通过给用户好处来刺激用户裂变分销，这就需要我们给用户生成专属的推广海报
因为小程序的用户uid是唯一的并且是不变的，所以我们后台大哥就以用户的uid作为生成专属二维码的图片名称，这里我们用canvas来绘制海报，废话不多说，上前端代码：
wxml:

view class='box'    canvas canvas-id='post' style='width:750rpx;height:1334rpx;'/canvas    view style='width:100%;text-align:center;color:#cc181d;font-size:24rpx;margin-top:15rpx;'这是您的专属二维码，将图片保存至手机后发朋友圈推广/view    button class='btn' bindtap='save'保存图片/button/view

js:

data: {    src1: 'https://www.qiaolibeilang.com/qrcode/',    src3: '.png',  },  onLoad: function (options) {    var that = this    var winWidth = wx.getSystemInfoSync().windowWidth;// 获取当前设备的可视宽度    var winHeight = wx.getSystemInfoSync().windowHeight;// 获取当前设备的可视高度    that.setData({      winWidth: winWidth,      winHeight: winHeight    })    let promise1 = new Promise(function (resolve, reject) {      wx.getImageInfo({        src: 'https://www.qiaolibeilang.com//public/uploads/images/20180809/free.png',        success: function (res) {          resolve(res);        }      })    });    let promise2 = new Promise(function (resolve, reject) {      var uid = wx.getStorageSync('uid')      console.log(uid)      wx.getImageInfo({        src: that.data.src1 + uid + that.data.src3,        success: function (res) {          resolve(res);        }      })    });    Promise.all([      promise1, promise2    ]).then(res = {      var that = this      var winWidth = wx.getSystemInfoSync().windowWidth;// 获取当前设备的可视宽度      var winHeight = wx.getSystemInfoSync().windowHeight;// 获取当前设备的可视高度      that.setData({        winWidth: winWidth,        winHeight: winHeight      })      console.log(winWidth)      console.log(winHeight)      const ctx = wx.createCanvasContext('post')      ctx.setFillStyle('red')      ctx.drawImage(res[0].path, 0, 0, that.data.winWidth, that.data.winWidth * 1.778)      ctx.drawImage(res[1].path, that.data.winWidth - 160, that.data.winWidth * 1.778 - 105, 80, 80)      console.log(res)      ctx.draw(true)    })  },  save: function (e) {    var that = this    wx.canvasToTempFilePath({      x: 0,      y: 0,      canvasId: 'post',      success: function (res) {        // 获得图片临时路径        console.log(res.tempFilePath)        wx.saveImageToPhotosAlbum({          filePath: res.tempFilePath,          success(res) {            console.log(res);            wx.showToast({              title: '保存成功',            });          },          fail(res) {            console.log("保存图片：fail");            console.log(res);          }        })      }    })  },

wxss代码就不写了，每个人风格都不一样，我的最终效果是就是这样，二维码是每个人单独的，剩下的就让后台去处理后续的业务逻辑就好了