Example code for canvas to implement QR code and image synthesis-H5 Tutorial-php.cn

Example code for canvas to implement QR code and image synthesis

青灯夜游

Release： 2018-10-09 16:26:57

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This article mainly introduces relevant information about the sample code for realizing QR code and image synthesis in canvas. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

The implementation idea is like this

Use jr-qrcode to generate url data:base64 for img use
Then use canvas to combine the two pictures into one picture

Problems encountered

After generating the picture, I found that the picture is very blurry , the solution is to double the canvas canvas and double the other parameters.

jr-qrcode You can use npm install --save jr-qrcode to install this package.

The function is Text can be converted to data:base64 for img's src use

The code is as follows:

import React, { Component } from &#39;react&#39;
const qrcode = require(&#39;jr-qrcode&#39;)
const loadImg = (src) => {
    const paths = Array.isArray(src) ? src : [src];
    const promise = [];
    paths.forEach((path) => {
        promise.push(new Promise((resolve, reject) => {
            let img = new Image();
            img.crossOrigin = "Anonymous";
            img.src = path;
            img.onload = () => {
                resolve(img);
            };
            img.onerror = (err) => {
                console.log(&#39;图片加载失败&#39;)
            }
        }))
    });
    return Promise.all(promise);

}
const getImageData = (url, src) => {
    const imgsrc = qrcode.getQrBase64(url)
    let canvas = document.createElement(&#39;canvas&#39;)
    const width = document.documentElement.clientWidth
    const height = document.documentElement.clientHeight
    canvas.width = width*2
    canvas.height = height*2
    let ctx = canvas.getContext("2d")
     loadImg([imgsrc, src]).then(([img1, img2]) => {
        ctx.drawImage(img2, 0, 0, width*2, height*2)
        ctx.drawImage(img1, width-80, height*2-220, 200, 160)
        ctx.fillStyle = &#39;rgba(0,0,0,0.3)&#39;;
        ctx.fillRect(width-80, height*2-60, 200, 40);
        ctx.save()
        ctx.font="28px Arial"
        ctx.fillStyle = &#39;#fff&#39;;
        ctx.fillText(&#39;长按识别二维码&#39;, width-80, height*2-30, 200, 160)
        let imageURL = canvas.toDataURL("image/png")
        document.getElementById(&#39;mix_img&#39;).setAttribute(&#39;src&#39;,imageURL)
    })
}
export default class QRcode extends Component {
    render() {
        const { url , picSrc} = this.props
        getImageData(url,picSrc)
        return (
            <p>
                <img  alt=&#39;mix_img&#39; id=&#39;mix_img&#39;/>
            </p>
        )
    }

}

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