@range3/holo/test/img2sixel.js

Hololive Tools for CLI

/**
 * Example script as cmdline converter.
 * Call: `node img2sixel.js <image files>`
 */

// set to 16 for xterm in VT340 mode
const MAX_PALETTE = 256

// 0 - default action (background color)
// 1 - keep previous content
// 2 - set background color
const BACKGROUND_SELECT = 0

const { loadImage, createCanvas } = require('canvas')
const { introducer, FINALIZER, sixelEncode, image2sixel } = require('sixel')
const hexdump = require('hexdump-nodejs')

async function processImage (filename, palLimit) {
  // load image
  let img
  try {
    img = await loadImage(filename)
  } catch (e) {
    console.error(`cannot load image "${filename}"`)
    return
  }
  console.log(img.width, img.height)
  const canvas = createCanvas(img.width, img.height)
  const ctx = canvas.getContext('2d')
  ctx.drawImage(img, 0, 0)

  // use image2sixel with internal quantizer
  const data = ctx.getImageData(0, 0, img.width, img.height).data
  console.log(`${filename}:`, data.length)
  // console.log(hexdump(data.slice(0, 128)))
  console.log(data.slice(0, 128))
  console.log(image2sixel(data, img.width, img.height, palLimit, BACKGROUND_SELECT))

  // alternatively use custom quantizer library
  // const RgbQuant = require('rgbquant');
  // const q = new RgbQuant({colors: palLimit, dithKern: 'FloydSteinberg', dithSerp: true});
  // q.sample(canvas);
  // const palette = q.palette(true);
  // const quantizedData = q.reduce(canvas);
  // console.log(`${filename}:`);
  // console.log([
  //   introducer(BACKGROUND_SELECT),
  //   sixelEncode(quantizedData, img.width, img.height, palette),
  //   FINALIZER
  // ].join(''));
}

async function main () {
  let palLimit = MAX_PALETTE
  for (const arg of process.argv) {
    if (arg.startsWith('-p')) {
      palLimit = parseInt(arg.slice(2))
      process.argv.splice(process.argv.indexOf(arg), 1)
      break
    }
  }
  for (const filename of process.argv.slice(2)) {
    await processImage(filename, palLimit)
  }
}

main()