Double-click Image Downloader

Double-click images to download them.

You will need to install an extension such as Tampermonkey, Greasemonkey or Violentmonkey to install this script.

You will need to install an extension such as Tampermonkey or Violentmonkey to install this script.

You will need to install an extension such as Tampermonkey or Violentmonkey to install this script.

You will need to install an extension such as Tampermonkey or Userscripts to install this script.

You will need to install an extension such as Tampermonkey to install this script.

You will need to install a user script manager extension to install this script.

(I already have a user script manager, let me install it!)

You will need to install an extension such as Stylus to install this style.

You will need to install an extension such as Stylus to install this style.

You will need to install an extension such as Stylus to install this style.

You will need to install a user style manager extension to install this style.

You will need to install a user style manager extension to install this style.

You will need to install a user style manager extension to install this style.

(I already have a user style manager, let me install it!)

// ==UserScript==
// @name        Double-click Image Downloader
// @namespace   leaumar
// @match       *://*/*
// @grant       GM.download
// @grant       GM.xmlHttpRequest
// @connect     *
// @version     3
// @author      [email protected]
// @description Double-click images to download them.
// @license     MPL-2.0
// @icon        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
// ==/UserScript==

class HttpError extends Error {
  constructor(verb, response) {
    super(`HTTP request ${verb}.`, {
      cause: response
    });
  }
}

function httpRequest(method, url) {
  return new Promise((resolve, reject) => {
    function fail(verb) {
      return error => reject(new HttpError(verb, error));
    }

    GM.xmlHttpRequest({
      url: url.href,
      onload: resolve,
      onerror: fail('errored'),
      onabort: fail('aborted'),
      ontimeout: fail('timed out'),
      responseType: 'blob',
    });
  });
}

function httpDownload(url, name) {
  return new Promise((resolve, reject) => {
    function fail(verb) {
      return error => reject(new HttpError(verb, error));
    }

    GM.download({
      url: url.href,
      name,
      onload: () => resolve(),
      onerror: fail('errored'),
      onabort: fail('aborted'),
      ontimeout: fail('timed out'),
      responseType: 'blob',
    });
  });
}

// -----------------

// from the greasemonkey docs
const lineSeparator = '\r\n';
const headerSeparator = ": ";

// is it still the 90s?
function parseHeaders(headersString) {
  return headersString.split(lineSeparator).reduce((accumulator, line) => {
    const pivot = line.indexOf(headerSeparator);
    const name = line.slice(0, pivot).trim().toLowerCase();
    const value = line.slice(pivot + headerSeparator.length).trim();
    accumulator[name] = value;
    return accumulator;
  }, {});
}

// ----------------

function filterFilename(name) {
  // foo.jpg
  return /^.+\.(?:jpe?g|png|gif|webp)$/iu.exec(name)?.[0];
}

async function queryFilename(url) {
  const response = await httpRequest('HEAD', url);
  const disposition = parseHeaders(response.responseHeaders)['content-disposition'];
  if (disposition != null) {
    // naive approach, but proper parsing is WAY overkill
    // attachment; filename="foo.jpg" -> foo.jpg
    const serverName = /^(?:attachment|inline)\s*;\s*filename="([^"]+)"/iu.exec(disposition)?.[1];
    if (serverName != null) {
      return filterFilename(serverName);
    }
  }
}

function readFilename(url) {
  const branch = url.pathname;
  const leaf = branch.slice(branch.lastIndexOf('/') + 1);
  return filterFilename(leaf);
}

function sleep(millis) {
    return new Promise(resolve => setTimeout(resolve, millis));
}

async function downloadImage(url, name, image) {
  const opacity = image.style.opacity ?? 1;

  image.style.opacity = 0.5;
  await Promise.all([httpDownload(url, name), sleep(100)]);
  image.style.opacity = opacity;
}

async function onDoubleClick(dblClick) {
  if (dblClick.target.nodeName === 'IMG') {
    const imageElement = dblClick.target;
    const url = new URL(imageElement.src, location.origin);
    const name = readFilename(url) ?? await queryFilename(url);
    if (name == null) {
      throw new Error('Could not determine a filename.');
    }
    await downloadImage(url, name, imageElement);
  }
}

(function main() {
  document.body.addEventListener('dblclick', dblClick => onDoubleClick(dblClick).catch(console.error));
})();