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YouTube Screenshot MacOS Download

Screenshot the current frame of any YouTube video and download it in high resolution
Ask a question, post a review, or report the script.
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// ==UserScript==
// @name         YouTube Screenshot MacOS Download
// @description  Screenshot the current frame of any YouTube video and download it in high resolution
// @version      1.6
// @icon         https://i.imgur.com/UbC1oPW.png
// @match        https://*.youtube.com/*
// @license      MIT
// @namespace    https://greasyfork.org/users/572660
// ==/UserScript==

let escapeHTMLPolicy = 'trustedTypes' in window
    ? trustedTypes.createPolicy('forceInner', { createHTML: html=>html })
    : { createHTML: html=>html };

function update(){
    let $miniplayerBtn = document.querySelector('button.ytp-miniplayer-button');
    if($miniplayerBtn && !$miniplayerBtn.previousElementSibling?.classList.contains('ytp-screenshot-button')){
        const $btn = document.createElement('button');
        $btn.id = 'ytp-screenshot-button';
        $btn.classList.add('ytp-screenshot-button', 'ytp-button');
        $btn.dataset.priority = '5';
        $btn.dataset.tooltipTargetId = 'ytp-screenshot-button';
        $btn.dataset.titleNoTooltip = 'Screenshot';
        $btn.ariaLabel = 'Screenshot';
        $btn.title = 'Screenshot';
        $btn.innerHTML = escapeHTMLPolicy.createHTML(`<svg height="100%" version="1.1" viewBox="-300 -1260 1560 1560" width="100%">
            <use class="ytp-svg-shadow" xlink:href="#ytp-id-screenshot-svg"></use>
            <path
                d="M200-120q-33 0-56.5-23.5T120-200v-560q0-33 23.5-56.5T200-840h560q33 0 56.5 23.5T840-760v560q0 33-23.5 56.5T760-120H200Zm0-80h560v-560H200v560Zm40-80h480L570-480 450-320l-90-120-120 160Zm-40 80v-560 560Z"
                fill="#fff" id="ytp-id-screenshot-svg"></path>
        </svg>`);
        $btn.addEventListener('click', screenshot);

        insertBefore($btn, $miniplayerBtn);
    }
    requestAnimationFrame(update);
}
requestAnimationFrame(update);

function insertBefore($element, $sibling){
    $sibling.parentElement.insertBefore($element, $sibling);
}

function screenshot(){
    const $video = document.querySelector('#player video, #movie_player video');
    if(!$video){
        console.error('No video found to screenshot!');
        return;
    }

    let wasPlaying = !$video.paused;
    if(wasPlaying) $video.pause();

    const $canvas = document.createElement('canvas');
    $canvas.width = $video.videoWidth;
    $canvas.height = $video.videoHeight;

    let oldCss = $video.style.cssText;
    $video.style.width = $video.videoWidth + 'px';
    $video.style.height = $video.videoHeight + 'px';

    const ctx = $canvas.getContext('2d');
    ctx.drawImage($video, 0, 0, $video.videoWidth, $video.videoHeight);

    $canvas.toBlob(blob=>{
        let url = URL.createObjectURL(blob);
        let a = document.createElement('a');
        a.style.display = 'none';
        a.href = url;
        a.download = document.title + '.png';
        document.body.appendChild(a);
        a.click();
        a.remove();
        URL.revokeObjectURL(url);

        $video.style.cssText = oldCss;
        $canvas.remove();
        if(wasPlaying) $video.play();
    });
}
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