回答

直接使用canvas画布合成

1、首先在wxml中输入一个canvas和一个现实最终海报的image

<canvas style="position:fixed;top: 0;left: -100%;" type="2d" id="Canvas"></canvas>
<image src="{{imgsrc}}" mode="aspectFit" ></image>

2、在onready中通过 wx.createSelectorQuery().select获取canvas画板及上下文context；

 /**
     * 生命周期函数--监听页面初次渲染完成
     */
    onReady() {
        const query = wx.createSelectorQuery()
        query.select('#Canvas')
            .fields({
                node: true,
                size: true
            })
            .exec((res) => {
                const canvas = res[0].node
                const ctx = canvas.getContext('2d')
                this.setData({
                    canvas,
                    ctx
                })
            })

    },

3、绘制海报和二维码

drawbg() {
        if (!this.data.canvas) return
        this.data.canvas.width = "300" //海报宽度
        this.data.canvas.height = "500" //海报高度
        const image = this.data.canvas.createImage();
        image.src = "/images/haibaobg.png";//海报背景图片
        image.onload = () => {
            // 将图片绘制到canvas上
            this.data.ctx.drawImage(image, 0, 0, 300, 500)//填充整个canvas画布
            this.drawqrcode();

        }
    },
    drawqrcode(){
        if (!this.data.canvas) return
        const image = this.data.canvas.createImage();
                image.src ="/images/qrcode.png";
                image.onload = () => {
                    // 将图片绘制到canvas上
                    this.data.ctx.drawImage(image, 100, 200, 50, 50)//绘制二维码图片到指定xy位置就好了
                    wx.canvasToTempFilePath({
                        canvas: this.data.canvas,
                        success: (res) => {
                            that.setData({
                                imgsrc: res.tempFilePath,
                                
                            })
                            //resolve(res.tempFilePath)
                        },
                    })
        
                }
    }