yomichan/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/>.
*/
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/**
* mediaUtility is an object containing helper methods related to media processing.
*/
const mediaUtility = (() => {
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/**
* 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 = /\.[^./\\]*$/.exec(path);
return match !== null ? match[0] : '';
}
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/**
* Gets an image file's media type using a file path.
* @param path The path to the file.
* @returns The media type string if it can be determined from the file path,
* otherwise null.
*/
function getImageMediaTypeFromFileName(path) {
switch (getFileNameExtension(path).toLowerCase()) {
case '.apng':
return 'image/apng';
case '.bmp':
return 'image/bmp';
case '.gif':
return 'image/gif';
case '.ico':
case '.cur':
return 'image/x-icon';
case '.jpg':
case '.jpeg':
case '.jfif':
case '.pjpeg':
case '.pjp':
return 'image/jpeg';
case '.png':
return 'image/png';
case '.svg':
return 'image/svg+xml';
case '.tif':
case '.tiff':
return 'image/tiff';
case '.webp':
return 'image/webp';
default:
return null;
}
}
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/**
* Attempts to load an image using a base64 encoded content and a media type.
* @param mediaType The media type for the image content.
* @param content The binary content for the image, encoded in base64.
* @returns A Promise which resolves with an HTMLImageElement instance on
* successful load, otherwise an error is thrown.
*/
function loadImageBase64(mediaType, content) {
return new Promise((resolve, reject) => {
const image = new Image();
const eventListeners = new EventListenerCollection();
eventListeners.addEventListener(image, 'load', () => {
eventListeners.removeAllEventListeners();
resolve(image);
}, false);
eventListeners.addEventListener(image, 'error', () => {
eventListeners.removeAllEventListeners();
reject(new Error('Image failed to load'));
}, false);
image.src = `data:${mediaType};base64,${content}`;
});
}
return {
getImageMediaTypeFromFileName,
loadImageBase64
};
})();