tweb-i2p/src/helpers/createPoster.ts

/*
 * https://github.com/morethanwords/tweb
 * Copyright (C) 2019-2021 Eduard Kuzmenko
 * https://github.com/morethanwords/tweb/blob/master/LICENSE
 */

import pause from "./schedulers/pause";
import { makeMediaSize } from "./mediaSize";
import scaleMediaElement from "./canvas/scaleMediaElement";
import preloadVideo from "./preloadVideo";

export function createPosterFromMedia(media: HTMLVideoElement | HTMLImageElement) {
  let width: number, height: number;
  if(media instanceof HTMLVideoElement) {
    width = media.videoWidth;
    height = media.videoHeight;
  } else {
    width = media.naturalWidth;
    height = media.naturalHeight;
  }

  return scaleMediaElement({
    media, 
    mediaSize: makeMediaSize(width, height), 
    boxSize: makeMediaSize(320, 240),
    quality: .9
  });
}

export function createPosterFromVideo(video: HTMLVideoElement): ReturnType<typeof scaleMediaElement> {
  return new Promise((resolve, reject) => {
    video.onseeked = () => {
      video.onseeked = () => {
        createPosterFromMedia(video).then(resolve);

        video.onseeked = undefined;
      };

      video.currentTime = 0;
    };
    
    video.onerror = reject;
    video.currentTime = Math.min(video.duration, 1);
  });
}

export async function createPosterForVideo(url: string) {
  const video = await preloadVideo(url);

  return Promise.race([
    pause(2000) as Promise<undefined>,
    createPosterFromVideo(video),
  ]);
}