how to download qrcode

[danjuanzzf]

how to download qrcode

[hjzheng]

1.Use dom API get the canvas object.
2.convert canvas to image.
3.Use a to download the image.

var link = document.createElement('a');
link.textContent = 'download image';

link.addEventListener('click', function(ev) {
    link.href = canvas.toDataURL();
    link.download = "mypainting.png";
}, false);

document.body.appendChild(link);

[danjuanzzf]

Thanks

[s875515]

download = () => { 
   const canvas: any = document.querySelector('.HpQrcode > canvas');
   this.downloadRef.href = canvas.toDataURL();
   this.downloadRef.download = 'mypainting.png';
}


<div className="HpQrcode">
  <QRCode
     value={copyLink}
     size={85}
     level={'H'}
  />
</div>

<a ref={(ref: any): any => this.downloadRef = ref}>
  download
</a>

[jutian88]

@s875515 thanks!

[Angelk90]

@hjzheng , @s875515 :
I should do something like this:

Inside a table (react-data-table-component), I have elements, one of these elements, the text must be converted into qr code, I thought I would use this module.

The problem that I need to convert the qr code into an image, I thought to simplify things based64.
Then I have to put this image in a pdf file that I need to generate.

How can I do?

It would be interesting if there was such a call:
QRCode.base64("text);
that returns the image of the qr code in base64.

You know how to give me advice.

[raffibag]

Adding to @hjzheng and @s875515's comments, I recently adapted the code above for use in a list view (table, screen shot attached) using React Router. The goal was to create a download component that received token and id props from which a QR code would be generated. This code uses React Router's <Link> API's innerRef: RefObject to get the underlying ref of the component.

import React, { Component } from 'react'
import QRCode from 'qrcode.react';
import { Link } from 'react-router-dom';

class Download extends Component {
  constructor(props) {
    super(props);
    this.serviceKey = props.serviceKey;
    this.token = props.token;
  }

  codeClassName = `QRCode-${this.props.serviceKey}`;

  refCallback(node){
    const nodeId = node.title;
    {/* use an html attribute (in this case, title) to get a unique id from the props passed to component */}
    const canvas: any = document.querySelector(`.QRCode-${nodeId} > canvas`);
    node.href = canvas.toDataURL();
    node.download = `TipGuru-QRCode-${nodeId}.png`;
  }

  render() {
    return (
      <div>
        {/* hide the QR code if there's no need to render in the view */}
        <div hidden className={this.codeClassName}>
          <QRCode
             value={this.token}
             size={1024}
          />
        </div>
        {/* Use html attributes to pass in any required data to the ref node. Note: target: '_blank' was required in order to initiate the download dialogue */}
        <Link to="/" target='_blank' title={this.serviceKey} innerRef={this.refCallback}>
            <i className="mdi mdi-download mdi-list-icon"></i>
        </Link>
      </div>
    )
  }
}

export { Download }

And here's the screenshot of the rendered view. The download is initiated when the download icon is clicked.

[iwarner]

This does not work when including a central image, any ideas on this?

      imageSettings={{
        src: ...,
        x: null,
        y: null,
        height: 36,
        width: 24,
        excavate: true
      }}

[glasperfan]

@iwarner for images, you have to be aware of CORS. My guess is you're seeing the tainted canvas security error?

@zpao mind if I add better support for CORS images? It's common when loading the image from a server, and it could be fixed by just creating an image with crossorigin="Anonymous" here (you'd need to programatically create the element, JSX won't ensure that the crossoriginattribute is set before the src attribute, see facebook/react#14035). That assumes the server returning the image has Access-Control-Allow-Origin in its response headers

[PetersonLian]

@iwarner for images, you have to be aware of CORS. My guess is you're seeing the tainted canvas security error?

@zpao mind if I add better support for CORS images? It's common when loading the image from a server, and it could be fixed by just creating an image with crossorigin="Anonymous" here (you'd need to programatically create the element, JSX won't ensure that the crossoriginattribute is set before the src attribute, see facebook/react#14035). That assumes the server returning the image has Access-Control-Allow-Origin in its response headers

@zpao supporting for CORS images is badly needed.

[ixqbar]

add crossOrigin: 'anonymous',

img = React.createElement("img", {
          src: imgSrc,
          crossOrigin: 'anonymous',
          style: {
            display: 'none'
          },
          onLoad: this.handleImageLoad,
          ref: function ref(_ref) {
            return _this2._image = _ref;
          }
        });

[Jedi-hongbin]

const qrcode = useRef(null);

点击保存

const saveQRCode = useCallback(() => {
const { firstChild: canvas }: any = qrcode!.current;
const href = canvas.toDataURL("image/png");
const link = document.createElement("a");
link.href = href;
link.download = xxxxx.png;
const event = new MouseEvent("click");
link.dispatchEvent(event);
}, []);

[Utzel-Butzel]

Here is a quick and dirty hack downloading the svg using ref on a div wrapper, since ref is not working on <QrCode /> and replacing the outlining <svg /> tag:

const svgRef = useRef();

function downloadBlob(blob, filename) {
   const objectUrl = URL.createObjectURL(blob);

   const link = document.createElement("a");
   link.href = objectUrl;
   link.download = filename;
   document.body.appendChild(link);
   link.click();
   document.body.removeChild(link);

   setTimeout(() => URL.revokeObjectURL(objectUrl), 5000);
}

const downloadSVG = useCallback(() => {
   const content = svgRef.current.children[0].innerHTML;
   const contentWithSvg = `<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1" height="128" width="128" viewBox="0 0 29 29">
${content}
</svg>`;
   const blob = new Blob([contentWithSvg], { type: "image/svg+xml" });
   downloadBlob(blob, `qrcode-${params.id}.svg`);
}, []);

 <div ref={svgRef}>
    <QRCode
      value={`${
        process.env.REACT_APP_WEB_BASE_URL
          ? process.env.REACT_APP_WEB_BASE_URL
          : window.location.href
      }preview/${params.id}`}
      renderAs={"svg"}
    />
 </div>
 <button onClick={downloadSVG}>Download</button>

[Rubyseher]

@s875515's solution results in Not allowed to navigate top frame to data URL error on modern versions/browsers. Here's a solution that worked:

const canvas = document.querySelector('.HpQrcode > canvas');
const pngFile = canvas.toDataURL("image/png");

const downloadLink = document.createElement("a");
downloadLink.download = "qrcode";
downloadLink.href = `${pngFile}`;
downloadLink.click();

[yaser-alazm]

I was looking for some tips for some other issue and @Utzel-Butzel suggestion really helped! Thanks.

[0529bill]

working Codesandbox using react and canvas!

working demo