added filter toggle button

- new `string-template` and `renderStringPref` (regex pattern matching) in chromium extension options
- new `cssInvertPage`, `cssInvertThumb`, and `cssInvertFilter` settings (with defaults; off by default)
  - available filters: `brightness()`, `contrast()`, `grayscale()`, `invert()`, `sepia()`, `saturate()`, and `hue-rotate()` via regex (valid CSS syntax)
- translations for `en-US`, `en-GB`, `en-CA`, and `de`
- filter influences PDF view container and PDF thmbnail container (thus also custom text/drawings/highlights)
- new svg as icon (modified `toolbarButton-editorStamp.svg`)
- button toggle is added next to zoom/scale controls in the middle of the toolbar

extensions/chromium/options/options.html

@@ -43,6 +43,15 @@ input:invalid {
 <div id="settings-boxes"></div>
 <button id="reset-button" type="button">Restore default settings</button>
 
+<template id="string-template">
+<div class="settings-row">
+  <label>
+    <span></span>
+    <input type="text" value="" pattern="" placeholder="">
+  </label>
+</div>
+</template>
+
 <template id="number-template">
 <div class="settings-row">
   <label>

extensions/chromium/options/options.js

@@ -105,6 +105,14 @@ Promise.all([
           "1",
           String(prefSchema.default)
         );
+      } else if (prefSchema.type === "string") {
+        renderPreference = renderStringPref(
+          prefSchema.title,
+          prefSchema.description,
+          prefName,
+          prefSchema.pattern,
+          prefSchema.default
+        );
       } else {
         // Should NEVER be reached. Only happens if a new type of preference is
         // added to the storage manifest.
@@ -212,6 +220,42 @@ function renderNumberPref(
   return renderPreference;
 }
 
+function renderStringPref(
+  shortDescription,
+  description,
+  prefName,
+  pattern,
+  placeholder
+) {
+  var wrapper = importTemplate("string-template");
+  var textInput = wrapper.querySelector("input");
+  textInput.pattern = pattern;
+  textInput.placeholder = placeholder;
+  textInput.oninput = function () {
+    textInput.setCustomValidity(
+      textInput.validity.patternMismatch
+        ? "Invalid value will not be saved!"
+        : ""
+    );
+  };
+  textInput.onchange = function () {
+    if (!textInput.reportValidity()) {
+      return;
+    }
+    var pref = {};
+    pref[prefName] = this.value;
+    storageArea.set(pref);
+  };
+  wrapper.querySelector("span").textContent = shortDescription;
+  wrapper.querySelector("label").title = description;
+  document.getElementById("settings-boxes").append(wrapper);
+
+  function renderPreference(value) {
+    textInput.value = value;
+  }
+  return renderPreference;
+}
+
 function renderBooleanPref(shortDescription, description, prefName) {
   var wrapper = importTemplate("checkbox-template");
   var checkbox = wrapper.querySelector('input[type="checkbox"]');

extensions/chromium/preferences_schema.json

@@ -8,6 +8,25 @@
       "enum": [0, 1, 2],
       "default": 2
     },
+    "cssInvertPage": {
+      "title": "Default brightness inversion",
+      "description": "Toggle on brightness inversion by default.",
+      "type": "boolean",
+      "default": false
+    },
+    "cssInvertThumb": {
+      "title": "Brightness invert thubnails",
+      "description": "Also apply brightness inversion for the page thubnails in the sidebar.",
+      "type": "boolean",
+      "default": true
+    },
+    "cssInvertFilter": {
+      "title": "Brightness inversion CSS filter",
+      "description": "The CSS filter used for the toggle. Available filters: 'brightness()', 'contrast()', 'grayscale()', 'invert()', 'sepia()', 'saturate()', and 'hue-rotate()'.",
+      "type": "string",
+      "pattern": "(?: *(?:brightness|contrast|grayscale|invert|sepia|saturate)\\( *(?:[+\\-]?(?:[0-9]+(?:\\.[0-9]+)?|[0-9]*\\.[0-9]+)(?:[eE][+\\-]?[0-9]+)?%? *)?\\)| *hue-rotate\\( *(?:0 *|[+\\-]?(?:[0-9]+(?:\\.[0-9]+)?|[0-9]*\\.[0-9]+)(?:[eE][+\\-]?[0-9]+)?(?:deg|g?rad|turn) *)?\\))+ *",
+      "default": "invert(90%) hue-rotate(180deg)"
+    },
     "showPreviousViewOnLoad": {
       "description": "DEPRECATED. Set viewOnLoad to 1 to disable showing the last page/position on load.",
       "type": "boolean",

l10n/de/viewer.ftl

@@ -30,6 +30,10 @@ pdfjs-zoom-in-button =
 pdfjs-zoom-in-button-label = Vergrößern
 pdfjs-zoom-select =
     .title = Zoom
+pdfjs-invert-button =
+    .title = Invertierte Helligkeit umschalten
+pdfjs-invert-button-label = Helligkeit umkehren
+    .title = Invert brightness
 pdfjs-presentation-mode-button =
     .title = In Präsentationsmodus wechseln
 pdfjs-presentation-mode-button-label = Präsentationsmodus

l10n/en-CA/viewer.ftl

@@ -30,6 +30,10 @@ pdfjs-zoom-in-button =
 pdfjs-zoom-in-button-label = Zoom In
 pdfjs-zoom-select =
     .title = Zoom
+pdfjs-invert-button =
+    .title = Toggle inverted brightness
+pdfjs-invert-button-label = Invert brightness
+    .title = Invert brightness
 pdfjs-presentation-mode-button =
     .title = Switch to Presentation Mode
 pdfjs-presentation-mode-button-label = Presentation Mode

l10n/en-GB/viewer.ftl

@@ -30,6 +30,10 @@ pdfjs-zoom-in-button =
 pdfjs-zoom-in-button-label = Zoom In
 pdfjs-zoom-select =
     .title = Zoom
+pdfjs-invert-button =
+    .title = Toggle inverted brightness
+pdfjs-invert-button-label = Invert brightness
+    .title = Invert brightness
 pdfjs-presentation-mode-button =
     .title = Switch to Presentation Mode
 pdfjs-presentation-mode-button-label = Presentation Mode

l10n/en-US/viewer.ftl

@@ -33,6 +33,10 @@ pdfjs-zoom-in-button =
 pdfjs-zoom-in-button-label = Zoom In
 pdfjs-zoom-select =
     .title = Zoom
+pdfjs-invert-button =
+    .title = Toggle inverted brightness
+pdfjs-invert-button-label = Invert brightness
+    .title = Invert brightness
 pdfjs-presentation-mode-button =
     .title = Switch to Presentation Mode
 pdfjs-presentation-mode-button-label = Presentation Mode

web/app.js

@@ -219,6 +219,8 @@ const PDFViewerApplication = {
       docStyle.setProperty("color-scheme", mode);
     }
 
+    onInvert.call(this);
+
     if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING")) {
       if (AppOptions.get("enableFakeMLManager")) {
         this.mlManager =
@@ -2019,6 +2021,7 @@ const PDFViewerApplication = {
     eventBus._on("zoomin", this.zoomIn.bind(this), opts);
     eventBus._on("zoomout", this.zoomOut.bind(this), opts);
     eventBus._on("zoomreset", this.zoomReset.bind(this), opts);
+    eventBus._on("invert", onInvert.bind(this), opts);
     eventBus._on("pagenumberchanged", onPageNumberChanged.bind(this), opts);
     eventBus._on(
       "scalechanged",
@@ -2445,6 +2448,17 @@ function onNamedAction(evt) {
   }
 }
 
+function onInvert(evt) {
+  // Handle brightness inversion (CSS filter) toggle
+  const active = evt?.state ?? AppOptions.get("cssInvertPage");
+  const filter = AppOptions.get("cssInvertFilter");
+  this.appConfig.toolbar.invert.classList.toggle("toggled", active);
+  this.appConfig.toolbar.invert.ariaChecked = String(active);
+  this.appConfig.viewerContainer.style.filter = active ? filter : "";
+  this.appConfig.sidebar.thumbnailView.style.filter =
+    active && AppOptions.get("cssInvertThumb") ? filter : "";
+}
+
 function onSidebarViewChanged({ view }) {
   this.pdfRenderingQueue.isThumbnailViewEnabled = view === SidebarView.THUMBS;
 

web/app_options.js

@@ -178,6 +178,21 @@ const defaultOptions = {
     value: 0,
     kind: OptionKind.VIEWER + OptionKind.PREFERENCE,
   },
+  cssInvertPage: {
+    /** @type {boolean} */
+    value: false,
+    kind: OptionKind.VIEWER + OptionKind.PREFERENCE,
+  },
+  cssInvertThumb: {
+    /** @type {boolean} */
+    value: true,
+    kind: OptionKind.VIEWER + OptionKind.PREFERENCE,
+  },
+  cssInvertFilter: {
+    /** @type {string} */
+    value: "invert(90%) hue-rotate(180deg)",
+    kind: OptionKind.VIEWER + OptionKind.PREFERENCE,
+  },
   debuggerSrc: {
     /** @type {string} */
     value: "./debugger.mjs",

web/images/toolbarButton-invert.svg

@@ -0,0 +1,12 @@
+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this
+   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
+<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 16 16" fill="black">
+  <path d="
+    M3 1a2 2 0 0 0-2 2v10a2 2 0 0 0 2 2h10a2 2 0 0 0 2-2v-10a2 2 0 0 0-2-2z
+    M5 12a1 1 0 0 1-1-1v-1.321a.75.75 0 0 1 .218-.529L6.35 7.005a.75.75 0 0 1 1.061-.003l2.112 2.102.612-.577a.75.75 0 0 1 1.047.017l.6.605a.75.75 0 0 1 .218.529L12 11a1 1 0 0 1-1 1z
+    M11.6 5m.4.4v1.2l-.4.4h-1.2l-.4-.4v-1.2l.4-.4h1.2z
+    M14 13l-1 1h-10l-1-1v-10l1-1h10l1 1z
+    M13.5 12.75l-.75.75h-9.5l-.75-.75v-9.5l.75-.75h9.5l.75.75z
+  " fill-rule="evenodd"/>
+</svg>

web/toolbar.js

@@ -38,6 +38,8 @@ import {
  * @property {HTMLButtonElement} next - Button to go to the next page.
  * @property {HTMLButtonElement} zoomIn - Button to zoom in the pages.
  * @property {HTMLButtonElement} zoomOut - Button to zoom out the pages.
+ * @property {HTMLButtonElement} invert - Button to toggle brightness inversion
+ *   (CSS filter).
  * @property {HTMLButtonElement} editorFreeTextButton - Button to switch to
  *   FreeText editing.
  * @property {HTMLButtonElement} download - Button to download the document.
@@ -67,6 +69,16 @@ class Toolbar {
       { element: options.zoomOut, eventName: "zoomout" },
       { element: options.print, eventName: "print" },
       { element: options.download, eventName: "download" },
+      {
+        element: options.invert,
+        eventName: "invert",
+        eventDetails: {
+          get state() {
+            const { classList } = options.invert;
+            return !classList.contains("toggled");
+          },
+        },
+      },
       {
         element: options.editorFreeTextButton,
         eventName: "switchannotationeditormode",

web/viewer.css

@@ -111,6 +111,7 @@
   --toolbarButton-pageDown-icon: url(images/toolbarButton-pageDown.svg);
   --toolbarButton-zoomOut-icon: url(images/toolbarButton-zoomOut.svg);
   --toolbarButton-zoomIn-icon: url(images/toolbarButton-zoomIn.svg);
+  --toolbarButton-invert-icon: url(images/toolbarButton-invert.svg);
   --toolbarButton-presentationMode-icon: url(images/toolbarButton-presentationMode.svg);
   --toolbarButton-print-icon: url(images/toolbarButton-print.svg);
   /*#if GENERIC*/
@@ -540,6 +541,10 @@ body {
   mask-image: var(--toolbarButton-zoomIn-icon);
 }
 
+#invertButton::before {
+  mask-image: var(--toolbarButton-invert-icon);
+}
+
 #editorFreeTextButton::before {
   mask-image: var(--toolbarButton-editorFreeText-icon);
 }

web/viewer.html

@@ -242,6 +242,9 @@ See https://github.com/adobe-type-tools/cmap-resources
                     <option value="4" data-l10n-id="pdfjs-page-scale-percent" data-l10n-args='{ "scale": 400 }'></option>
                   </select>
                 </span>
+                <button id="invertButton" class="toolbarButton" type="button" tabindex="0" data-l10n-id="pdfjs-invert-button" role="checkbox" aria-checked="false">
+                  <span data-l10n-id="pdfjs-invert-button-label"></span>
+                </button>
               </div>
               <div id="toolbarViewerRight" class="toolbarHorizontalGroup">
                 <div id="editorModeButtons" class="toolbarHorizontalGroup" role="radiogroup">

web/viewer.js

@@ -44,6 +44,7 @@ function getViewerConfiguration() {
       next: document.getElementById("next"),
       zoomIn: document.getElementById("zoomInButton"),
       zoomOut: document.getElementById("zoomOutButton"),
+      invert: document.getElementById("invertButton"),
       print: document.getElementById("printButton"),
       editorFreeTextButton: document.getElementById("editorFreeTextButton"),
       editorFreeTextParamsToolbar: document.getElementById(