109 lines
3.4 KiB
TypeScript
109 lines
3.4 KiB
TypeScript
let filterSupport: boolean | undefined;
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/**
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* Checks context filter support.
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*
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* @returns {boolean} True if the filter is supported and false if the filter is not supported by the browser.
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*/
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export function checkBlurSupport() {
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if (typeof filterSupport === 'undefined') {
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const canvas = document.createElement('canvas');
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const ctx = canvas.getContext('2d');
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filterSupport = typeof ctx?.filter !== 'undefined';
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canvas.remove();
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}
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return filterSupport;
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}
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/**
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* Convert blob to base64.
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*
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* @param {Blob} blob - The link to add info with.
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* @returns {Promise<string>}
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*/
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export const blobToData = (blob: Blob) =>
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new Promise(resolve => {
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const reader = new FileReader();
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reader.onloadend = () => resolve(reader.result?.toString());
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reader.readAsDataURL(blob);
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});
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/**
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* Convert blob to base64.
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*
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* @param {string} url - The image url.
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* @returns {Object} - Returns the converted blob to base64.
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*/
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export const toDataURL = async (url: string) => {
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const response = await fetch(url);
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const blob = await response.blob();
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const resData = await blobToData(blob);
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return resData;
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};
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/**
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* Resize image and adjust original aspect ratio.
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*
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* @param {Object} base64image - Base64 image extraction.
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* @param {number} width - Value for resizing the image width.
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* @param {number} height - Value for resizing the image height.
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* @returns {Promise<string>}
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*
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*/
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export function resizeImage(base64image: any, width = 1920, height = 1080): Promise<string> {
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// In order to work on Firefox browser we need to handle the asynchronous nature of image loading; We need to use
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// a promise mechanism. The reason why it 'works' without this mechanism in Chrome is actually 'by accident' because
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// the image happens to be in the cache and the browser is able to deliver the uncompressed/decoded image
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// before using the image in the drawImage call.
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return new Promise(resolve => {
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const img = document.createElement('img');
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img.onload = function() {
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// Create an off-screen canvas.
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const canvas = document.createElement('canvas');
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// Set its dimension to target size.
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const context = canvas.getContext('2d');
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canvas.width = width;
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canvas.height = height;
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// Draw source image into the off-screen canvas.
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// TODO: keep aspect ratio and implement object-fit: cover.
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context?.drawImage(img as any, 0, 0, width, height);
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// Encode image to data-uri with base64 version of compressed image.
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resolve(canvas.toDataURL('image/jpeg', 0.5));
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};
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img.src = base64image;
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});
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}
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/**
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* Creating a wrapper for promises on a specific time interval.
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*
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* @param {number} milliseconds - The number of milliseconds to wait the specified
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* {@code promise} to settle before automatically rejecting the returned
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* {@code Promise}.
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* @param {Promise} promise - The {@code Promise} for which automatic rejecting
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* after the specified timeout is to be implemented.
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* @returns {Promise}
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*/
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export function timeout(milliseconds: number, promise: Promise<any>): Promise<Object> {
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return new Promise((resolve, reject) => {
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setTimeout(() => {
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reject(new Error('408'));
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return;
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}, milliseconds);
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promise.then(resolve, reject);
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});
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}
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