forked from treehouse/mastodon
67 lines
1.7 KiB
JavaScript
67 lines
1.7 KiB
JavaScript
const MAX_IMAGE_DIMENSION = 1280;
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const getImageUrl = inputFile => new Promise((resolve, reject) => {
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if (window.URL && URL.createObjectURL) {
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try {
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resolve(URL.createObjectURL(inputFile));
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} catch (error) {
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reject(error);
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}
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return;
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}
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const reader = new FileReader();
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reader.onerror = (...args) => reject(...args);
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reader.onload = ({ target }) => resolve(target.result);
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reader.readAsDataURL(inputFile);
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});
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const loadImage = inputFile => new Promise((resolve, reject) => {
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getImageUrl(inputFile).then(url => {
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const img = new Image();
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img.onerror = (...args) => reject(...args);
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img.onload = () => resolve(img);
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img.src = url;
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}).catch(reject);
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});
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export default inputFile => new Promise((resolve, reject) => {
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if (!inputFile.type.match(/image.*/) || inputFile.type === 'image/gif') {
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resolve(inputFile);
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return;
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}
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loadImage(inputFile).then(img => {
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const canvas = document.createElement('canvas');
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const { width, height } = img;
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let newWidth, newHeight;
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if (width < MAX_IMAGE_DIMENSION && height < MAX_IMAGE_DIMENSION) {
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resolve(inputFile);
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return;
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}
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if (width > height) {
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newHeight = height * MAX_IMAGE_DIMENSION / width;
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newWidth = MAX_IMAGE_DIMENSION;
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} else if (height > width) {
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newWidth = width * MAX_IMAGE_DIMENSION / height;
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newHeight = MAX_IMAGE_DIMENSION;
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} else {
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newWidth = MAX_IMAGE_DIMENSION;
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newHeight = MAX_IMAGE_DIMENSION;
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}
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canvas.width = newWidth;
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canvas.height = newHeight;
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canvas.getContext('2d').drawImage(img, 0, 0, newWidth, newHeight);
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canvas.toBlob(resolve, inputFile.type);
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}).catch(reject);
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});
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