rmqr/index.js

Rectangular Micro QR code generator for node

const sharp = require('sharp');

const strategy = {
  balanced: 0,
  'min-height': 1,
  minHeight: 1,
  'min-width': 2,
  minWidth: 2
}

const correction = {
  auto: 0,
  medium: 1,
  high: 2
}

class rMQR {
  async generate(text, options={}) {
    if ((typeof text).toLowerCase() !== 'string') {
      throw new Error('Expected String recived instance of '+typeof text);
    }
    if (text.length < 1) {
      throw new Error('Input must be atleast one letter');
    }
    if (text.length > (150 - (options?.correction === correction.high ? 76 : 0))) {
      throw new Error('Input is too long');
    }
    if (options.strategy) {
      if (!Object.values(strategy).includes(options.strategy)) {
        throw new Error('Unknown strategy');
      }
    }
    if (options.correction) {
      if (!Object.values(correction).includes(options.correction)) {
        throw new Error('Unknown correction');
      }
    }

    // Fetch for now because implementing the whole qr specification is a *bit* hard
    let req = await fetch('https://asia-northeast1-rmqr-generator.cloudfunctions.net/generate-rmqr-code', {
      method: 'POST',
      headers: {
        'content-type': 'application/json'
      },
      body: JSON.stringify({
        text: text,
        versionStrategy: ['balanced','minimize_height','minimize_width'][options?.strategy ?? 0],
        errorCorrectionLevel: ['auto','m','h'][options?.correction ?? 0]
      })
    });
    let res = await req.json();
    return res;
  }
  toImage(data, format='png', type='buffer', size=8) {
    let alias = {
      jpg: 'jpeg'
    }
    if (Object.keys(alias).includes(format)) format = alias[format];
    return new Promise((resolve, reject) => {
      let qr = new sharp(Buffer.from(data.qr.flat().map(p=>!p*255)), {
        raw: {
          width: data.width,
          height: data.height,
          channels: 1
        }
      })
        .toFormat(format)
        .resize(data.width*size, data.height*size, {
          kernel: sharp.kernel.nearest
        })
        .toBuffer()
        .then(outputBuffer => {
          Object.keys(alias).map(key => {alias[alias[key]] = key; delete alias[key]});
          if (Object.keys(alias).includes(format)) format = alias[format];
          switch (type) {
            case 'buffer':
              resolve(outputBuffer);
              break;
            case 'uri':
              resolve(`data:image/${format};base64,${outputBuffer.toString('base64')}`);
              break;
            default:
              reject('Unsoported type');
              break;
          }
        })
        .catch(err=>{
          reject(err);
        })
    });
  }
}

module.exports = {
  rmqr: rMQR,
  strategy: strategy,
  correction: correction
}