145a5a8a8d
* Conform more code to strict null checking * Conform more code to strict null checking * Iterate * Iterate
124 lines
4.4 KiB
TypeScript
124 lines
4.4 KiB
TypeScript
/*
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Copyright 2022 The Matrix.org Foundation C.I.C.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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import { BlurhashEncoder } from "../BlurhashEncoder";
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import { IEncryptedFile } from "../customisations/models/IMediaEventContent";
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type ThumbnailableElement = HTMLImageElement | HTMLVideoElement;
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export const BLURHASH_FIELD = "xyz.amorgan.blurhash"; // MSC2448
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interface IThumbnail {
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info: {
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thumbnail_info?: {
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w: number;
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h: number;
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mimetype: string;
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size: number;
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};
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w: number;
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h: number;
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[BLURHASH_FIELD]?: string;
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thumbnail_url?: string;
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thumbnail_file?: IEncryptedFile;
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};
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thumbnail: Blob;
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}
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const MAX_WIDTH = 800;
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const MAX_HEIGHT = 600;
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/**
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* Create a thumbnail for a image DOM element.
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* The image will be smaller than MAX_WIDTH and MAX_HEIGHT.
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* The thumbnail will have the same aspect ratio as the original.
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* Draws the element into a canvas using CanvasRenderingContext2D.drawImage
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* Then calls Canvas.toBlob to get a blob object for the image data.
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*
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* Since it needs to calculate the dimensions of the source image and the
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* thumbnailed image it returns an info object filled out with information
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* about the original image and the thumbnail.
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*
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* @param {HTMLElement} element The element to thumbnail.
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* @param {number} inputWidth The width of the image in the input element.
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* @param {number} inputHeight the width of the image in the input element.
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* @param {string} mimeType The mimeType to save the blob as.
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* @param {boolean} calculateBlurhash Whether to calculate a blurhash of the given image too.
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* @return {Promise} A promise that resolves with an object with an info key
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* and a thumbnail key.
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*/
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export async function createThumbnail(
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element: ThumbnailableElement,
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inputWidth: number,
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inputHeight: number,
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mimeType: string,
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calculateBlurhash = true,
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): Promise<IThumbnail> {
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let targetWidth = inputWidth;
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let targetHeight = inputHeight;
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if (targetHeight > MAX_HEIGHT) {
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targetWidth = Math.floor(targetWidth * (MAX_HEIGHT / targetHeight));
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targetHeight = MAX_HEIGHT;
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}
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if (targetWidth > MAX_WIDTH) {
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targetHeight = Math.floor(targetHeight * (MAX_WIDTH / targetWidth));
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targetWidth = MAX_WIDTH;
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}
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let canvas: HTMLCanvasElement | OffscreenCanvas;
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let context: CanvasRenderingContext2D | OffscreenCanvasRenderingContext2D;
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try {
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canvas = new window.OffscreenCanvas(targetWidth, targetHeight);
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context = canvas.getContext("2d") as OffscreenCanvasRenderingContext2D;
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} catch (e) {
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// Fallback support for other browsers (Safari and Firefox for now)
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canvas = document.createElement("canvas");
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canvas.width = targetWidth;
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canvas.height = targetHeight;
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context = canvas.getContext("2d")!;
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}
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context.drawImage(element, 0, 0, targetWidth, targetHeight);
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let thumbnailPromise: Promise<Blob>;
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if (window.OffscreenCanvas && canvas instanceof OffscreenCanvas) {
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thumbnailPromise = canvas.convertToBlob({ type: mimeType });
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} else {
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thumbnailPromise = new Promise<Blob>((resolve) =>
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(canvas as HTMLCanvasElement).toBlob(resolve as BlobCallback, mimeType),
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);
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}
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const imageData = context.getImageData(0, 0, targetWidth, targetHeight);
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// thumbnailPromise and blurhash promise are being awaited concurrently
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const blurhash = calculateBlurhash ? await BlurhashEncoder.instance.getBlurhash(imageData) : undefined;
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const thumbnail = await thumbnailPromise;
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return {
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info: {
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thumbnail_info: {
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w: targetWidth,
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h: targetHeight,
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mimetype: thumbnail.type,
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size: thumbnail.size,
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},
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w: inputWidth,
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h: inputHeight,
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[BLURHASH_FIELD]: blurhash,
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},
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thumbnail,
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};
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}
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