import ImageEncoder from './ImageEncoder';
import stream from 'stream';

import Png from 'png';

/**
 * An ImageEncoder implementation which uses 'node-png' module
 * which is a binary (C-based) module.
 */
export default class NodePngImageEncoder extends ImageEncoder {
  public write(
    image: Buffer,
    width: number,
    height: number
  ): Promise<stream.Readable> {
    const png = new Png(image, width, height, 'gray', 8);
    const out = new stream.PassThrough();
    return new Promise(resolve => {
      png.encode(function(png_data: any): void {
        out.end(png_data);
        resolve(out);
      });
    });
  }
}