Code for generating images in WeChat mini program

The content of this article is about the code for generating images in the WeChat applet. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

Add canvas

First of all, you need to use the 5ba626b379994d53f7acf72a64f9b697 component to perform drawing operations in the mini program. The steps are roughly divided into the following three parts: A large background image, a dynamic text ('title user name and other information'), and a small program code image. Then we first put the following 5ba626b379994d53f7acf72a64f9b697 in our wxml code:

<!--wxml代码-->
<view style=&#39;width:100%;height:100%;&#39; bindlongpress=&#39;saveInviteCard&#39;>
  <canvas canvas-id="shareCanvas" style="width:{{windowWidth}}px;height:{{windowHeight}}px" ></canvas>
</view>

Third-party function introduction

const util = require('../../utils/util.js')

//util.js
var Promise = require('../components/bluebird.min.js')

module.exports = {
  promisify: api => {
    return (options, ...params) => {
      return new Promise((resolve, reject) => {
        const extras = {
          success: resolve,
          fail: reject
        }
        api({ ...options, ...extras }, ...params)
      })
    }
  }
}

bluebird.min.js You can download it from Baidu yourself, the source file The code is too long, so I won't copy and paste it here.

//获取手机宽高 
wx.getSystemInfo({
    success: function (res) {
      wc.put('phoneInfo', res)
    }
  });

var windowHeight = phoneInfo.windowHeight, windowWidth = phoneInfo.windowWidth
self.setData({
   windowHeight: windowHeight,
   windowWidth: windowWidth
 })

//在这段代码中，我们通过使用wx.getImageInfo这个API来下载一个网络图片到本地（并可获取该图片的尺寸等其他信息），然后调用ctx.drawImage方法将图片绘制到画布上，填满画布。

const wxGetImageInfo = util.promisify(wx.getImageInfo)
//绘制二维码
Promise.all([
      //背景图
      wxGetImageInfo({
        src: 'https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1536213812443&di=753a0a49acfd390fba9fd7884daafa5c&imgtype=0&src=http%3A%2F%2Fi5.hexunimg.cn%2F2016-08-10%2F185422031.jpg'
      }),
      //二维码
      wxGetImageInfo({
        src: 'https://ss0.bdstatic.com/70cFuHSh_Q1YnxGkpoWK1HF6hhy/it/u=1898297765,3486952215&fm=26&gp=0.jpg'
      })
    ]).then(res => {
      console.log(res)
      if (res[0].errMsg == "getImageInfo:ok" && res[1].errMsg == "getImageInfo:ok"){
        const ctx = wx.createCanvasContext('shareCanvas')

        // 底图
        ctx.drawImage(res[0].path, 0, 0, windowWidth, windowHeight)

        //写入文字
        ctx.setTextAlign('center')    // 文字居中
        ctx.setFillStyle('#f3a721')  // 文字颜色：黑色
        ctx.setFontSize(22)         // 文字字号：22px
        ctx.fillText("作者：墜夢—Eric", windowWidth / 2, windowHeight / 2)

        // 小程序码
        const qrImgSize = 150
        ctx.drawImage(res[1].path, (windowWidth - qrImgSize) / 2, windowHeight / 1.8, qrImgSize, qrImgSize)

        ctx.stroke()
        ctx.draw()
      }else{
        wx.showToast({
          title: '邀请卡绘制失败!',
          image:'../../asset/images/warning.png'
        })
      }
 })

In this way, our sharing picture is almost generated.

Long press the picture to save it to the system album

To save it into the user's system album, to achieve this function, we mainly rely on wx.canvasToTempFilePath and wx.saveImageToPhotosAlbumThese two APIs.

The main process is to first generate a temporary file from the image drawn on 5ba626b379994d53f7acf72a64f9b697 through wx.canvasToTempFilePath, and then through wx. saveImageToPhotosAlbumPerforms the operation of saving to the system album.

  //保存邀请卡
  saveInviteCard:function(){
    console.log('保存图片')
    const wxCanvasToTempFilePath = util.promisify(wx.canvasToTempFilePath)
    const wxSaveImageToPhotosAlbum = util.promisify(wx.saveImageToPhotosAlbum)

    wxCanvasToTempFilePath({
      canvasId: 'shareCanvas'
    }, this).then(res => {
      return wxSaveImageToPhotosAlbum({
        filePath: res.tempFilePath
      })
    }).then(res => {
      wx.showToast({
        title: '已保存到相册'
      })
    })
  }

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