Merge pull request #446 from toasted-nutbread/dictionary-images

Dictionary images

16 files changed, 645 insertions, 9 deletions

diff --git a/ext/bg/background.html b/ext/bg/background.html
index afe9c5d1..f1006f8d 100644
--- a/ext/bg/background.html
+++ b/ext/bg/background.html
@@ -36,6 +36,7 @@
         <script src="/bg/js/handlebars.js"></script>
         <script src="/bg/js/japanese.js"></script>
         <script src="/bg/js/json-schema.js"></script>
+        <script src="/bg/js/media-utility.js"></script>
         <script src="/bg/js/options.js"></script>
         <script src="/bg/js/profile-conditions.js"></script>
         <script src="/bg/js/request.js"></script>
diff --git a/ext/bg/data/dictionary-term-bank-v3-schema.json b/ext/bg/data/dictionary-term-bank-v3-schema.json
index bb982e36..4790e561 100644
--- a/ext/bg/data/dictionary-term-bank-v3-schema.json
+++ b/ext/bg/data/dictionary-term-bank-v3-schema.json
@@ -31,8 +31,85 @@
                 "type": "array",
                 "description": "Array of definitions for the term/expression.",
                 "items": {
-                    "type": "string",
-                    "description": "Single definition for the term/expression."
+                    "oneOf": [
+                        {
+                            "type": "string",
+                            "description": "Single definition for the term/expression."
+                        },
+                        {
+                            "type": "object",
+                            "description": "Single detailed definition for the term/expression.",
+                            "required": [
+                                "type"
+                            ],
+                            "properties": {
+                                "type": {
+                                    "type": "string",
+                                    "description": "The type of the data for this definition.",
+                                    "enum": ["text", "image"]
+                                }
+                            },
+                            "oneOf": [
+                                {
+                                    "required": [
+                                        "type",
+                                        "text"
+                                    ],
+                                    "additionalProperties": false,
+                                    "properties": {
+                                        "type": {
+                                            "type": "string",
+                                            "enum": ["text"]
+                                        },
+                                        "text": {
+                                            "type": "string",
+                                            "description": "Single definition for the term/expression."
+                                        }
+                                    }
+                                },
+                                {
+                                    "required": [
+                                        "type",
+                                        "path"
+                                    ],
+                                    "additionalProperties": false,
+                                    "properties": {
+                                        "type": {
+                                            "type": "string",
+                                            "enum": ["image"]
+                                        },
+                                        "path": {
+                                            "type": "string",
+                                            "description": "Path to the image file in the archive."
+                                        },
+                                        "width": {
+                                            "type": "integer",
+                                            "description": "Preferred width of the image.",
+                                            "minimum": 1
+                                        },
+                                        "height": {
+                                            "type": "integer",
+                                            "description": "Preferred width of the image.",
+                                            "minimum": 1
+                                        },
+                                        "title": {
+                                            "type": "string",
+                                            "description": "Hover text for the image."
+                                        },
+                                        "description": {
+                                            "type": "string",
+                                            "description": "Description of the image."
+                                        },
+                                        "pixelated": {
+                                            "type": "boolean",
+                                            "description": "Whether or not the image should appear pixelated at sizes larger than the image's native resolution.",
+                                            "default": false
+                                        }
+                                    }
+                                }
+                            ]
+                        }
+                    ]
                 }
             },
             {
diff --git a/ext/bg/js/backend.js b/ext/bg/js/backend.js
index e0814c17..8a19203f 100644
--- a/ext/bg/js/backend.js
+++ b/ext/bg/js/backend.js
@@ -111,7 +111,8 @@ class Backend {
             ['getAnkiModelFieldNames', {handler: this._onApiGetAnkiModelFieldNames.bind(this), async: true}],
             ['getDictionaryInfo', {handler: this._onApiGetDictionaryInfo.bind(this), async: true}],
             ['getDictionaryCounts', {handler: this._onApiGetDictionaryCounts.bind(this), async: true}],
-            ['purgeDatabase', {handler: this._onApiPurgeDatabase.bind(this), async: true}]
+            ['purgeDatabase', {handler: this._onApiPurgeDatabase.bind(this), async: true}],
+            ['getMedia', {handler: this._onApiGetMedia.bind(this), async: true}]
         ]);
 
         this._commandHandlers = new Map([
@@ -762,6 +763,10 @@ class Backend {
         return await this.translator.purgeDatabase();
     }
 
+    async _onApiGetMedia({targets}) {
+        return await this.database.getMedia(targets);
+    }
+
     // Command handlers
 
     async _onCommandSearch(params) {
diff --git a/ext/bg/js/database.js b/ext/bg/js/database.js
index 260c815a..16612403 100644
--- a/ext/bg/js/database.js
+++ b/ext/bg/js/database.js
@@ -33,7 +33,7 @@ class Database {
         }
 
         try {
-            this.db = await Database._open('dict', 5, (db, transaction, oldVersion) => {
+            this.db = await Database._open('dict', 6, (db, transaction, oldVersion) => {
                 Database._upgrade(db, transaction, oldVersion, [
                     {
                         version: 2,
@@ -90,6 +90,15 @@ class Database {
                                 indices: ['dictionary', 'expression', 'reading', 'sequence', 'expressionReverse', 'readingReverse']
                             }
                         }
+                    },
+                    {
+                        version: 6,
+                        stores: {
+                            media: {
+                                primaryKey: {keyPath: 'id', autoIncrement: true},
+                                indices: ['dictionary', 'path']
+                            }
+                        }
                     }
                 ]);
             });
@@ -268,6 +277,34 @@ class Database {
         return result;
     }
 
+    async getMedia(targets) {
+        this._validate();
+
+        const count = targets.length;
+        const promises = [];
+        const results = new Array(count).fill(null);
+        const createResult = Database._createMedia;
+        const processRow = (row, [index, dictionaryName]) => {
+            if (row.dictionary === dictionaryName) {
+                results[index] = createResult(row, index);
+            }
+        };
+
+        const transaction = this.db.transaction(['media'], 'readonly');
+        const objectStore = transaction.objectStore('media');
+        const index = objectStore.index('path');
+
+        for (let i = 0; i < count; ++i) {
+            const {path, dictionaryName} = targets[i];
+            const only = IDBKeyRange.only(path);
+            promises.push(Database._getAll(index, only, [i, dictionaryName], processRow));
+        }
+
+        await Promise.all(promises);
+
+        return results;
+    }
+
     async getDictionaryInfo() {
         this._validate();
 
@@ -432,6 +469,10 @@ class Database {
         return {character, mode, data, dictionary, index};
     }
 
+    static _createMedia(row, index) {
+        return Object.assign({}, row, {index});
+    }
+
     static _getAll(dbIndex, query, context, processRow) {
         const fn = typeof dbIndex.getAll === 'function' ? Database._getAllFast : Database._getAllUsingCursor;
         return fn(dbIndex, query, context, processRow);
diff --git a/ext/bg/js/dictionary-importer.js b/ext/bg/js/dictionary-importer.js
index bf6809ec..3727f7ee 100644
--- a/ext/bg/js/dictionary-importer.js
+++ b/ext/bg/js/dictionary-importer.js
@@ -18,6 +18,7 @@
 /* global
  * JSZip
  * JsonSchema
+ * mediaUtility
  * requestJson
  */
 
@@ -148,6 +149,22 @@ class DictionaryImporter {
             }
         }
 
+        // Extended data support
+        const extendedDataContext = {
+            archive,
+            media: new Map()
+        };
+        for (const entry of termList) {
+            const glossaryList = entry.glossary;
+            for (let i = 0, ii = glossaryList.length; i < ii; ++i) {
+                const glossary = glossaryList[i];
+                if (typeof glossary !== 'object' || glossary === null) { continue; }
+                glossaryList[i] = await this._formatDictionaryTermGlossaryObject(glossary, extendedDataContext, entry);
+            }
+        }
+
+        const media = [...extendedDataContext.media.values()];
+
         // Add dictionary
         const summary = this._createSummary(dictionaryTitle, version, index, {prefixWildcardsSupported});
 
@@ -188,6 +205,7 @@ class DictionaryImporter {
         await bulkAdd('kanji', kanjiList);
         await bulkAdd('kanjiMeta', kanjiMetaList);
         await bulkAdd('tagMeta', tagList);
+        await bulkAdd('media', media);
 
         return {result: summary, errors};
     }
@@ -275,4 +293,76 @@ class DictionaryImporter {
 
         return [termBank, termMetaBank, kanjiBank, kanjiMetaBank, tagBank];
     }
+
+    async _formatDictionaryTermGlossaryObject(data, context, entry) {
+        switch (data.type) {
+            case 'text':
+                return data.text;
+            case 'image':
+                return await this._formatDictionaryTermGlossaryImage(data, context, entry);
+            default:
+                throw new Error(`Unhandled data type: ${data.type}`);
+        }
+    }
+
+    async _formatDictionaryTermGlossaryImage(data, context, entry) {
+        const dictionary = entry.dictionary;
+        const {path, width: preferredWidth, height: preferredHeight, title, description, pixelated} = data;
+        if (context.media.has(path)) {
+            // Already exists
+            return data;
+        }
+
+        let errorSource = entry.expression;
+        if (entry.reading.length > 0) {
+            errorSource += ` (${entry.reading});`;
+        }
+
+        const file = context.archive.file(path);
+        if (file === null) {
+            throw new Error(`Could not find image at path ${JSON.stringify(path)} for ${errorSource}`);
+        }
+
+        const content = await file.async('base64');
+        const mediaType = mediaUtility.getImageMediaTypeFromFileName(path);
+        if (mediaType === null) {
+            throw new Error(`Could not determine media type for image at path ${JSON.stringify(path)} for ${errorSource}`);
+        }
+
+        let image;
+        try {
+            image = await mediaUtility.loadImageBase64(mediaType, content);
+        } catch (e) {
+            throw new Error(`Could not load image at path ${JSON.stringify(path)} for ${errorSource}`);
+        }
+
+        const width = image.naturalWidth;
+        const height = image.naturalHeight;
+
+        // Create image data
+        const mediaData = {
+            dictionary,
+            path,
+            mediaType,
+            width,
+            height,
+            content
+        };
+        context.media.set(path, mediaData);
+
+        // Create new data
+        const newData = {
+            type: 'image',
+            path,
+            width,
+            height
+        };
+        if (typeof preferredWidth === 'number') { newData.preferredWidth = preferredWidth; }
+        if (typeof preferredHeight === 'number') { newData.preferredHeight = preferredHeight; }
+        if (typeof title === 'string') { newData.title = title; }
+        if (typeof description === 'string') { newData.description = description; }
+        if (typeof pixelated === 'boolean') { newData.pixelated = pixelated; }
+
+        return newData;
+    }
 }
diff --git a/ext/bg/js/media-utility.js b/ext/bg/js/media-utility.js
new file mode 100644
index 00000000..1f93b2b4
--- /dev/null
+++ b/ext/bg/js/media-utility.js
@@ -0,0 +1,98 @@
+/*
+ * 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
+    };
+})();
diff --git a/ext/bg/search.html b/ext/bg/search.html
index eacc1893..fe88e264 100644
--- a/ext/bg/search.html
+++ b/ext/bg/search.html
@@ -85,6 +85,7 @@
         <script src="/mixed/js/display-context.js"></script>
         <script src="/mixed/js/display.js"></script>
         <script src="/mixed/js/display-generator.js"></script>
+        <script src="/mixed/js/media-loader.js"></script>
         <script src="/mixed/js/scroll.js"></script>
         <script src="/mixed/js/text-scanner.js"></script>
         <script src="/mixed/js/template-handler.js"></script>
diff --git a/ext/fg/float.html b/ext/fg/float.html
index 3ccf68eb..c8ea9b67 100644
--- a/ext/fg/float.html
+++ b/ext/fg/float.html
@@ -51,6 +51,7 @@
         <script src="/mixed/js/display-context.js"></script>
         <script src="/mixed/js/display.js"></script>
         <script src="/mixed/js/display-generator.js"></script>
+        <script src="/mixed/js/media-loader.js"></script>
         <script src="/mixed/js/scroll.js"></script>
         <script src="/mixed/js/template-handler.js"></script>
 
diff --git a/ext/mixed/css/display-dark.css b/ext/mixed/css/display-dark.css
index e4549bbf..acfa2782 100644
--- a/ext/mixed/css/display-dark.css
+++ b/ext/mixed/css/display-dark.css
@@ -94,3 +94,10 @@ h2 { border-bottom-color: #2f2f2f; }
 #term-pitch-accent-graph-dot-downstep>circle:last-of-type {
     fill: #ffffff;
 }
+
+.term-glossary-image-container {
+    background-color: #2f2f2f;
+}
+.term-glossary-image-container-overlay {
+    color: #888888;
+}
diff --git a/ext/mixed/css/display-default.css b/ext/mixed/css/display-default.css
index 7bcb1014..70f81eb6 100644
--- a/ext/mixed/css/display-default.css
+++ b/ext/mixed/css/display-default.css
@@ -94,3 +94,10 @@ h2 { border-bottom-color: #eeeeee; }
 #term-pitch-accent-graph-dot-downstep>circle:last-of-type {
     fill: #000000;
 }
+
+.term-glossary-image-container {
+    background-color: #eeeeee;
+}
+.term-glossary-image-container-overlay {
+    color: #777777;
+}
diff --git a/ext/mixed/css/display.css b/ext/mixed/css/display.css
index d1a54064..4f43af6f 100644
--- a/ext/mixed/css/display.css
+++ b/ext/mixed/css/display.css
@@ -611,6 +611,121 @@ button.action-button {
     stroke-width: 5;
 }
 
+.term-glossary-image-container {
+    display: inline-block;
+    white-space: nowrap;
+    max-width: 100%;
+    position: relative;
+    vertical-align: top;
+    line-height: 0;
+    font-size: 0.07142857em; /* 14px => 1px */
+    overflow: hidden;
+}
+
+.term-glossary-image-link {
+    cursor: inherit;
+    color: inherit;
+}
+
+.term-glossary-image-link[href]:hover {
+    cursor: pointer;
+}
+
+.term-glossary-image-container-overlay {
+    position: absolute;
+    left: 0;
+    top: 0;
+    width: 100%;
+    height: 100%;
+    font-size: 14em; /* 1px => 14px; */
+    line-height: 1.42857143; /* 14px => 20px */
+    display: table;
+    table-layout: fixed;
+    white-space: normal;
+}
+
+.term-glossary-item[data-has-image=true][data-image-load-state=load-error] .term-glossary-image-container-overlay:after {
+    content: "Image failed to load";
+    display: table-cell;
+    width: 100%;
+    height: 100%;
+    vertical-align: middle;
+    text-align: center;
+    padding: 0.25em;
+}
+
+.term-glossary-image {
+    display: inline-block;
+    position: absolute;
+    left: 0;
+    top: 0;
+    width: 100%;
+    height: 100%;
+    vertical-align: top;
+    object-fit: contain;
+    border: none;
+    outline: none;
+}
+
+.term-glossary-image:not([src]) {
+    display: none;
+}
+
+.term-glossary-image[data-pixelated=true] {
+    image-rendering: auto;
+    image-rendering: -moz-crisp-edges;
+    image-rendering: -webkit-optimize-contrast;
+    image-rendering: pixelated;
+    image-rendering: crisp-edges;
+}
+
+.term-glossary-image-aspect-ratio-sizer {
+    content: "";
+    display: inline-block;
+    width: 0;
+    vertical-align: top;
+    font-size: 0;
+}
+
+.term-glossary-image-link-text:before {
+    content: "[";
+}
+
+.term-glossary-image-link-text:after {
+    content: "]";
+}
+
+:root[data-compact-glossaries=true] .term-glossary-image-container {
+    display: none;
+    position: absolute;
+    left: 0;
+    top: 100%;
+    z-index: 1;
+}
+
+:root[data-compact-glossaries=true] .entry:nth-last-of-type(1):not(:nth-of-type(1)) .term-glossary-image-container {
+    bottom: 100%;
+    top: auto;
+}
+
+:root[data-compact-glossaries=true] .term-glossary-image-link {
+    position: relative;
+    display: inline-block;
+}
+
+:root[data-compact-glossaries=true] .term-glossary-image-link:hover .term-glossary-image-container,
+:root[data-compact-glossaries=true] .term-glossary-image-link:focus .term-glossary-image-container {
+    display: block;
+}
+
+:root:not([data-compact-glossaries=true]) .term-glossary-image-link-text {
+    display: none;
+}
+
+:root:not([data-compact-glossaries=true]) .term-glossary-image-description {
+    display: block;
+}
+
 
 /*
  * Kanji
diff --git a/ext/mixed/display-templates.html b/ext/mixed/display-templates.html
index 3baa8293..fc0558a9 100644
--- a/ext/mixed/display-templates.html
+++ b/ext/mixed/display-templates.html
@@ -35,6 +35,7 @@
 </li></template>
 <template id="term-definition-disambiguation-template"><span class="term-definition-disambiguation"></span></template>
 <template id="term-glossary-item-template"><li class="term-glossary-item"><span class="term-glossary-separator"> </span><span class="term-glossary"></span></li></template>
+<template id="term-glossary-item-image-template"><li class="term-glossary-item" data-has-image="true"><span class="term-glossary-separator"> </span><span class="term-glossary"><a class="term-glossary-image-link" target="_blank" rel="noreferrer noopener"><span class="term-glossary-image-container"><span class="term-glossary-image-aspect-ratio-sizer"></span><img class="term-glossary-image" alt="" /><span class="term-glossary-image-container-overlay"></span></span><span class="term-glossary-image-link-text">Image</span></a> <span class="term-glossary-image-description"></span></span></li></template>
 <template id="term-reason-template"><span class="term-reason"></span><span class="term-reason-separator"> </span></template>
 
 <template id="term-pitch-accent-static-template"><svg xmlns="http://www.w3.org/2000/svg" style="display: none;">
diff --git a/ext/mixed/js/api.js b/ext/mixed/js/api.js
index c97dc687..52f41646 100644
--- a/ext/mixed/js/api.js
+++ b/ext/mixed/js/api.js
@@ -140,6 +140,10 @@ function apiPurgeDatabase() {
     return _apiInvoke('purgeDatabase');
 }
 
+function apiGetMedia(targets) {
+    return _apiInvoke('getMedia', {targets});
+}
+
 function _apiInvoke(action, params={}) {
     const data = {action, params};
     return new Promise((resolve, reject) => {
diff --git a/ext/mixed/js/display-generator.js b/ext/mixed/js/display-generator.js
index 0f991362..a2b2b139 100644
--- a/ext/mixed/js/display-generator.js
+++ b/ext/mixed/js/display-generator.js
@@ -22,7 +22,8 @@
  */
 
 class DisplayGenerator {
-    constructor() {
+    constructor({mediaLoader}) {
+        this._mediaLoader = mediaLoader;
         this._templateHandler = null;
         this._termPitchAccentStaticTemplateIsSetup = false;
     }
@@ -176,16 +177,30 @@ class DisplayGenerator {
         const onlyListContainer = node.querySelector('.term-definition-disambiguation-list');
         const glossaryContainer = node.querySelector('.term-glossary-list');
 
-        node.dataset.dictionary = details.dictionary;
+        const dictionary = details.dictionary;
+        node.dataset.dictionary = dictionary;
 
         this._appendMultiple(tagListContainer, this._createTag.bind(this), details.definitionTags);
         this._appendMultiple(onlyListContainer, this._createTermDisambiguation.bind(this), details.only);
-        this._appendMultiple(glossaryContainer, this._createTermGlossaryItem.bind(this), details.glossary);
+        this._appendMultiple(glossaryContainer, this._createTermGlossaryItem.bind(this), details.glossary, dictionary);
 
         return node;
     }
 
-    _createTermGlossaryItem(glossary) {
+    _createTermGlossaryItem(glossary, dictionary) {
+        if (typeof glossary === 'string') {
+            return this._createTermGlossaryItemText(glossary);
+        } else if (typeof glossary === 'object' && glossary !== null) {
+            switch (glossary.type) {
+                case 'image':
+                    return this._createTermGlossaryItemImage(glossary, dictionary);
+            }
+        }
+
+        return null;
+    }
+
+    _createTermGlossaryItemText(glossary) {
         const node = this._templateHandler.instantiate('term-glossary-item');
         const container = node.querySelector('.term-glossary');
         if (container !== null) {
@@ -194,6 +209,68 @@ class DisplayGenerator {
         return node;
     }
 
+    _createTermGlossaryItemImage(data, dictionary) {
+        const {path, width, height, preferredWidth, preferredHeight, title, description, pixelated} = data;
+
+        const usedWidth = (
+            typeof preferredWidth === 'number' ?
+            preferredWidth :
+            width
+        );
+        const aspectRatio = (
+            typeof preferredWidth === 'number' &&
+            typeof preferredHeight === 'number' ?
+            preferredWidth / preferredHeight :
+            width / height
+        );
+
+        const node = this._templateHandler.instantiate('term-glossary-item-image');
+        node.dataset.path = path;
+        node.dataset.dictionary = dictionary;
+        node.dataset.imageLoadState = 'not-loaded';
+
+        const imageContainer = node.querySelector('.term-glossary-image-container');
+        imageContainer.style.width = `${usedWidth}em`;
+        if (typeof title === 'string') {
+            imageContainer.title = title;
+        }
+
+        const aspectRatioSizer = node.querySelector('.term-glossary-image-aspect-ratio-sizer');
+        aspectRatioSizer.style.paddingTop = `${aspectRatio * 100.0}%`;
+
+        const image = node.querySelector('img.term-glossary-image');
+        const imageLink = node.querySelector('.term-glossary-image-link');
+        image.dataset.pixelated = `${pixelated === true}`;
+
+        if (this._mediaLoader !== null) {
+            this._mediaLoader.loadMedia(
+                path,
+                dictionary,
+                (url) => this._setImageData(node, image, imageLink, url, false),
+                () => this._setImageData(node, image, imageLink, null, true)
+            );
+        }
+
+        if (typeof description === 'string') {
+            const container = node.querySelector('.term-glossary-image-description');
+            this._appendMultilineText(container, description);
+        }
+
+        return node;
+    }
+
+    _setImageData(container, image, imageLink, url, unloaded) {
+        if (url !== null) {
+            image.src = url;
+            imageLink.href = url;
+            container.dataset.imageLoadState = 'loaded';
+        } else {
+            image.removeAttribute('src');
+            imageLink.removeAttribute('href');
+            container.dataset.imageLoadState = unloaded ? 'unloaded' : 'load-error';
+        }
+    }
+
     _createTermDisambiguation(disambiguation) {
         const node = this._templateHandler.instantiate('term-definition-disambiguation');
         node.dataset.term = disambiguation;
diff --git a/ext/mixed/js/display.js b/ext/mixed/js/display.js
index c2284ffe..9587ec3b 100644
--- a/ext/mixed/js/display.js
+++ b/ext/mixed/js/display.js
@@ -20,6 +20,7 @@
  * DOM
  * DisplayContext
  * DisplayGenerator
+ * MediaLoader
  * WindowScroll
  * apiAudioGetUri
  * apiBroadcastTab
@@ -62,7 +63,8 @@ class Display {
         this.clickScanPrevent = false;
         this.setContentToken = null;
 
-        this.displayGenerator = new DisplayGenerator();
+        this.mediaLoader = new MediaLoader();
+        this.displayGenerator = new DisplayGenerator({mediaLoader: this.mediaLoader});
         this.windowScroll = new WindowScroll();
 
         this._onKeyDownHandlers = new Map([
@@ -479,6 +481,8 @@ class Display {
         const token = {}; // Unique identifier token
         this.setContentToken = token;
         try {
+            this.mediaLoader.unloadAll();
+
             switch (type) {
                 case 'terms':
                     await this.setContentTerms(details.definitions, details.context, token);
diff --git a/ext/mixed/js/media-loader.js b/ext/mixed/js/media-loader.js
new file mode 100644
index 00000000..64ccd715
--- /dev/null
+++ b/ext/mixed/js/media-loader.js
@@ -0,0 +1,107 @@
+/*
+ * 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/>.
+ */
+
+/* global
+ * apiGetMedia
+ */
+
+class MediaLoader {
+    constructor() {
+        this._token = {};
+        this._mediaCache = new Map();
+        this._loadMediaData = [];
+    }
+
+    async loadMedia(path, dictionaryName, onLoad, onUnload) {
+        const token = this.token;
+        const data = {onUnload, loaded: false};
+
+        this._loadMediaData.push(data);
+
+        const media = await this.getMedia(path, dictionaryName);
+        if (token !== this.token) { return; }
+
+        onLoad(media.url);
+        data.loaded = true;
+    }
+
+    unloadAll() {
+        for (const {onUnload, loaded} of this._loadMediaData) {
+            if (typeof onUnload === 'function') {
+                onUnload(loaded);
+            }
+        }
+        this._loadMediaData = [];
+
+        for (const map of this._mediaCache.values()) {
+            for (const {url} of map.values()) {
+                if (url !== null) {
+                    URL.revokeObjectURL(url);
+                }
+            }
+        }
+        this._mediaCache.clear();
+
+        this._token = {};
+    }
+
+    async getMedia(path, dictionaryName) {
+        let cachedData;
+        let dictionaryCache = this._mediaCache.get(dictionaryName);
+        if (typeof dictionaryCache !== 'undefined') {
+            cachedData = dictionaryCache.get(path);
+        } else {
+            dictionaryCache = new Map();
+            this._mediaCache.set(dictionaryName, dictionaryCache);
+        }
+
+        if (typeof cachedData === 'undefined') {
+            cachedData = {
+                promise: null,
+                data: null,
+                url: null
+            };
+            dictionaryCache.set(path, cachedData);
+            cachedData.promise = this._getMediaData(path, dictionaryName, cachedData);
+        }
+
+        return cachedData.promise;
+    }
+
+    async _getMediaData(path, dictionaryName, cachedData) {
+        const token = this._token;
+        const data = (await apiGetMedia([{path, dictionaryName}]))[0];
+        if (token === this._token && data !== null) {
+            const contentArrayBuffer = this._base64ToArrayBuffer(data.content);
+            const blob = new Blob([contentArrayBuffer], {type: data.mediaType});
+            const url = URL.createObjectURL(blob);
+            cachedData.data = data;
+            cachedData.url = url;
+        }
+        return cachedData;
+    }
+
+    _base64ToArrayBuffer(content) {
+        const binaryContent = window.atob(content);
+        const length = binaryContent.length;
+        const array = new Uint8Array(length);
+        for (let i = 0; i < length; ++i) {
+            array[i] = binaryContent.charCodeAt(i);
+        }
+        return array.buffer;
+    }
+}