heic-convert/lib.js

const jpegJs = require('jpeg-js');
const { PNG } = require('pngjs');

module.exports = decode => {
  const to = {
    JPEG: ({ data, width, height, quality }) => jpegJs.encode({ data, width, height }, quality).data,
    PNG: ({ data, width, height }) => {
      const png = new PNG({ width, height });
      png.data = data;

      return PNG.sync.write(png, {
        width: width,
        height: height,
        deflateLevel: 9,
        deflateStrategy: 3,
        filterType: -1,
        colorType: 6,
        inputHasAlpha: true
      });
    }
  };

  const convertImage = async ({ image, format, quality }) => {
    return await to[format]({
      width: image.width,
      height: image.height,
      data: image.data,
      quality: Math.floor(quality * 100)
    });
  };

  const convert = async ({ buffer, format, quality, all }) => {
    if (!to[format]) {
      throw new Error(`output format needs to be one of [${Object.keys(to)}]`);
    }

    if (!all) {
      const image = await decode({ buffer });
      return await convertImage({ image, format, quality });
    }

    const images = await decode.all({ buffer });

    return images.map(image => {
      return {
        convert: async () => await convertImage({
          image: await image.decode(),
          format,
          quality
        })
      };
    });
  };

  return {
    one: async ({ buffer, format, quality = 0.92 }) => await convert({ buffer, format, quality, all: false }),
    all: async ({ buffer, format, quality = 0.92 }) => await convert({ buffer, format, quality, all: true })
  };
};