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diff --git a/ext/bg/js/media-utility.js b/ext/bg/js/media-utility.js
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+++ b/ext/bg/js/media-utility.js
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+/*
+ * Copyright (C) 2020  Yomichan Authors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/**
+ * mediaUtility is an object containing helper methods related to media processing.
+ */
+const mediaUtility = (() => {
+    /**
+     * Gets the file extension of a file path. URL search queries and hash
+     * fragments are not handled.
+     * @param path The path to the file.
+     * @returns The file extension, including the '.', or an empty string
+     *   if there is no file extension.
+     */
+    function getFileNameExtension(path) {
+        const match = /\.[^./\\]*$/.exec(path);
+        return match !== null ? match[0] : '';
+    }
+
+    /**
+     * Gets an image file's media type using a file path.
+     * @param path The path to the file.
+     * @returns The media type string if it can be determined from the file path,
+     *   otherwise null.
+     */
+    function getImageMediaTypeFromFileName(path) {
+        switch (getFileNameExtension(path).toLowerCase()) {
+            case '.apng':
+                return 'image/apng';
+            case '.bmp':
+                return 'image/bmp';
+            case '.gif':
+                return 'image/gif';
+            case '.ico':
+            case '.cur':
+                return 'image/x-icon';
+            case '.jpg':
+            case '.jpeg':
+            case '.jfif':
+            case '.pjpeg':
+            case '.pjp':
+                return 'image/jpeg';
+            case '.png':
+                return 'image/png';
+            case '.svg':
+                return 'image/svg+xml';
+            case '.tif':
+            case '.tiff':
+                return 'image/tiff';
+            case '.webp':
+                return 'image/webp';
+            default:
+                return null;
+        }
+    }
+
+    /**
+     * Attempts to load an image using a base64 encoded content and a media type.
+     * @param mediaType The media type for the image content.
+     * @param content The binary content for the image, encoded in base64.
+     * @returns A Promise which resolves with an HTMLImageElement instance on
+     *   successful load, otherwise an error is thrown.
+     */
+    function loadImageBase64(mediaType, content) {
+        return new Promise((resolve, reject) => {
+            const image = new Image();
+            const eventListeners = new EventListenerCollection();
+            eventListeners.addEventListener(image, 'load', () => {
+                eventListeners.removeAllEventListeners();
+                resolve(image);
+            }, false);
+            eventListeners.addEventListener(image, 'error', () => {
+                eventListeners.removeAllEventListeners();
+                reject(new Error('Image failed to load'));
+            }, false);
+            image.src = `data:${mediaType};base64,${content}`;
+        });
+    }
+
+    return {
+        getImageMediaTypeFromFileName,
+        loadImageBase64
+    };
+})();