114 lines
3.1 KiB
JavaScript
114 lines
3.1 KiB
JavaScript
import EXIF from 'exif-js';
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const MAX_IMAGE_PIXELS = 1638400; // 1280x1280px
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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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const getOrientation = (img, type = 'image/png') => new Promise(resolve => {
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if (type !== 'image/jpeg') {
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resolve(1);
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return;
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}
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EXIF.getData(img, () => {
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const orientation = EXIF.getTag(img, 'Orientation');
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resolve(orientation);
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});
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});
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const processImage = (img, { width, height, orientation, type = 'image/png' }) => new Promise(resolve => {
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const canvas = document.createElement('canvas');
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if (4 < orientation && orientation < 9) {
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canvas.width = height;
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canvas.height = width;
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} else {
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canvas.width = width;
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canvas.height = height;
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}
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const context = canvas.getContext('2d');
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switch (orientation) {
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case 2: context.transform(-1, 0, 0, 1, width, 0); break;
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case 3: context.transform(-1, 0, 0, -1, width, height); break;
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case 4: context.transform(1, 0, 0, -1, 0, height); break;
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case 5: context.transform(0, 1, 1, 0, 0, 0); break;
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case 6: context.transform(0, 1, -1, 0, height, 0); break;
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case 7: context.transform(0, -1, -1, 0, height, width); break;
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case 8: context.transform(0, -1, 1, 0, 0, width); break;
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}
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context.drawImage(img, 0, 0, width, height);
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// The Tor Browser and maybe other browsers may prevent reading from canvas
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// and return an all-white image instead. Assume reading failed if the resized
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// image is perfectly white.
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const imageData = context.getImageData(0, 0, width, height);
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if (imageData.data.every(value => value === 255)) {
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throw 'Failed to read from canvas';
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}
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canvas.toBlob(resolve, type);
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});
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const resizeImage = (img, type = 'image/png') => new Promise((resolve, reject) => {
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const { width, height } = img;
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const newWidth = Math.round(Math.sqrt(MAX_IMAGE_PIXELS * (width / height)));
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const newHeight = Math.round(Math.sqrt(MAX_IMAGE_PIXELS * (height / width)));
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getOrientation(img, type)
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.then(orientation => processImage(img, {
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width: newWidth,
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height: newHeight,
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orientation,
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type,
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}))
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.then(resolve)
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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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if (img.width * img.height < MAX_IMAGE_PIXELS) {
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resolve(inputFile);
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return;
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}
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resizeImage(img, inputFile.type)
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.then(resolve)
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.catch(() => resolve(inputFile));
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}).catch(reject);
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});
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