zpao/qrcode.react

qrcode.react

A React component to generate QR codes for rendering to the DOM.

Installation

npm install qrcode.react

Usage

qrcode.react exports two components, supporting rendering as SVG or Canvas. SVG is generally recommended as it is more flexible, but Canvas may be preferable.

All examples are shown using modern JavaScript modules and syntax. CommonJS require('qrcode.react') is also supported.

QRCodeSVG

import ReactDOM from 'react-dom';
import {QRCodeSVG} from 'qrcode.react';

ReactDOM.render(
  <QRCodeSVG value="https://reactjs.org/" />,
  document.getElementById('mountNode')
);

QRCodeCanvas

import ReactDOM from 'react-dom';
import {QRCodeCanvas} from 'qrcode.react';

ReactDOM.render(
  <QRCodeCanvas value="https://reactjs.org/" />,
  document.getElementById('mountNode')
);

Available Props

Below is a condensed type definition of the props QRCodeSVG and QRCodeCanvas accept.

type QRProps = {
  /**
   * The value to encode into the QR Code. An array of strings can be passed in
   * to represent multiple segments to further optimize the QR Code.
   */
  value: string | string[];
  /**
   * The size, in pixels, to render the QR Code.
   * @defaultValue 128
   */
  size?: number;
  /**
   * The Error Correction Level to use.
   * @see https://www.qrcode.com/en/about/error_correction.html
   * @defaultValue L
   */
  level?: 'L' | 'M' | 'Q' | 'H';
  /**
   * The background color used to render the QR Code.
   * @see https://developer.mozilla.org/en-US/docs/Web/CSS/color_value
   * @defaultValue #FFFFFF
   */
  bgColor?: string;
  /**
   * The foreground color used to render the QR Code.
   * @see https://developer.mozilla.org/en-US/docs/Web/CSS/color_value
   * @defaultValue #000000
   */
  fgColor?: string;
  /**
   * Whether or not a margin of 4 modules should be rendered as a part of the
   * QR Code.
   * @deprecated Use `marginSize` instead.
   * @defaultValue false
   */
  includeMargin?: boolean;
  /**
   * The number of _modules_ to use for margin. The QR Code specification
   * requires `4`, however you can specify any number. Values will be turned to
   * integers with `Math.floor`. Overrides `includeMargin` when both are specified.
   * @defaultValue 0
   */
  marginSize?: number;
  /**
   * The title to assign to the QR Code. Used for accessibility reasons.
   */
  title?: string;
  /**
   * The minimum version used when encoding the QR Code. Valid values are 1-40
   * with higher values resulting in more complex QR Codes. The optimal
   * (lowest) version is determined for the `value` provided, using `minVersion`
   * as the lower bound.
   * @defaultValue 1
   */
  minVersion?: number;
  /**
   * If enabled, the Error Correction Level of the result may be higher than
   * the specified Error Correction Level option if it can be done without
   * increasing the version.
   * @defaultValue true
   */
  boostLevel?: boolean;
  /**
   * The settings for the embedded image.
   */
  imageSettings?: {
    /**
     * The URI of the embedded image.
     */
    src: string;
    /**
     * The height, in pixels, of the image.
     */
    height: number;
    /**
     * The width, in pixels, of the image.
     */
    width: number;
    /**
     * Whether or not to "excavate" the modules around the embedded image. This
     * means that any modules the embedded image overlaps will use the background
     * color.
     */
    excavate: boolean;
    /**
     * The horiztonal offset of the embedded image, starting from the top left corner.
     * Will center if not specified.
     */
    x?: number;
    /**
     * The vertical offset of the embedded image, starting from the top left corner.
     * Will center if not specified.
     */
    y?: number;
    /**
     * The opacity of the embedded image in the range of 0-1.
     * @defaultValue 1
     */
    opacity?: number;
    /**
     * The cross-origin value to use when loading the image. This is used to
     * ensure compatibility with CORS, particularly when extracting image data
     * from QRCodeCanvas.
     * Note: `undefined` is treated differently than the seemingly equivalent
     * empty string. This is intended to align with HTML behavior where omitting
     * the attribute behaves differently than the empty string.
     */
    crossOrigin?: 'anonymous' | 'use-credentials' | '' | undefined;
  };
};

value

The value to encode into the QR Code. See Encoding Mode for additional details.

size

The size, in pixels, to render the QR Code.

level

The Error Correction Level to use. Information is encoded in QR Codes such that they can lose part of their visible areas and still be decodable. The amount of correction depends on this value. Higher error correction will result in more complex QR Codes.

• L = low (~7%)
• M = medium (~15%)
• Q = quartile (~25%)
• H = high (~30%)

See Wikipedia or the official QR Code documentation for a more detailed explaination.

bgColor

The background color used to render the QR Code. This is passed directly to the Canvas (ctx.fillStyle = bgColor) or the SVG <path> (fill={bgColor}), both which accept any CSS color.

fgColor

The foreground color used to render the QR Code. It follows the same constraints as bgColor

includeMargin

[!WARNING] This has been deprecated in v4 and will be removed in a future version. Use marginSize instead.

Whether or not a margin of 4 modules should be rendered as a part of the QR Code.

marginSize

The number of modules to use for margin. The QR Code specification requires 4, however you can specify any number. Values will be turned to integers with Math.floor. Overrides includeMargin when both are specified.

title

The title to assign to the QR Code. Used for accessibility reasons.

minVersion

The minimum version used when encoding the QR Code. Valid values are 1-40 with higher values resulting in more complex QR Codes. The optimal (lowest) version is determined for the value provided, using minVersion as the lower bound.

boostLevel

If enabled, the Error Correction Level of the result may be higher than the specified Error Correction Level option if it can be done without increasing the version.

imageSettings

Used to specify the details for an embedded image, often used to embed a logo.

imageSettings.src

The URI of the embedded image. This will get passed directly to src of an img element for QRCodeCanvas or the href of an inline image for QRCodeSVG.

imageSettings.height

The height, in pixels, of the embedded image.

imageSettings.width

The width, in pixels, of the embedded image.

imageSettings.excavate

Whether or not to "excavate" the modules around the embedded image. This means that any modules the embedded image overlaps will use the background color. Use this to ensure clean edges around your image. It is also useful when embedding images with transparency.

imageSettings.x

The horizontal offset, in pixels, of the embedded image. Positioning follows standard DOM positioning, with top left corner being 0.

When not specified, will center the image.

imageSettings.y

The vertical offset, in pixels, of the embedded image. Positioning follows standard DOM positioning, with top left corner being 0.

When not specified, will center the image.

imageSettings.opacity

The opacity of the embedded image, in the range of 0 to 1.

imageSettings.crossOrigin

The cross-origin value to use when loading the embedded image. Note that undefined works as typically does with React, excluding the attribute from the DOM node. This is intended to align with HTML behavior where omitting the attribute behaves differently than the empty string.

Custom Styles

qrcode.react will pass through any additional props to the underlying DOM node (<svg> or <canvas>). This allows the use of inline style or custom className to customize the rendering. One common use would be to support a responsive layout.

[!NOTE] In order to render QR Codes in <canvas> on high density displays, we scale the canvas element to contain an appropriate number of pixels and then use inline styles to scale back down. We will merge any additional styles, with custom height and width overriding our own values. This allows scaling to percentages but if scaling beyond the size, you will encounter blurry images. I recommend detecting resizes with something like react-measure to detect and pass the appropriate size when rendering to <canvas>.

Encoding Mode

qrcode.react supports encoding text only. Prior to v4.1.0, this was done in a single segment. Since then, the value prop can be an array of strings. Each member will be encoded separately. The encoding library being used does minimal detection to determine if each segment being encoded can follow an optimized path for Numeric or Alphanumeric modes, allowing for more data to be encoded. Otherwise, it will encode following Byte mode. This mode includes supports multi-byte Unicode characters such as Kanji, however it does not support the optimized Kanji encoding mode.

LICENSE

qrcode.react is licensed under the ISC license.

qrcode.react bundles QR Code Generator, which is available under the MIT license.