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import EXIF from 'exif-js';
const MAX_IMAGE_PIXELS = 2073600; // 1920x1080px
const _browser_quirks = {};
// Some browsers will automatically draw images respecting their EXIF orientation
// while others won't, and the safest way to detect that is to examine how it
// is done on a known image.
// See https://github.com/w3c/csswg-drafts/issues/4666
// and https://github.com/blueimp/JavaScript-Load-Image/commit/1e4df707821a0afcc11ea0720ee403b8759f3881
const dropOrientationIfNeeded = (orientation) => new Promise(resolve => {
switch (_browser_quirks['image-orientation-automatic']) {
case true:
resolve(1);
break;
case false:
resolve(orientation);
break;
default:
// black 2x1 JPEG, with the following meta information set:
// - EXIF Orientation: 6 (Rotated 90° CCW)
const testImageURL =
'data:image/jpeg;base64,/9j/4QAiRXhpZgAATU0AKgAAAAgAAQESAAMAAAABAAYAAAA' +
'AAAD/2wCEAAEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBA' +
'QEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQE' +
'BAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAf/AABEIAAEAAgMBEQACEQEDEQH/x' +
'ABKAAEAAAAAAAAAAAAAAAAAAAALEAEAAAAAAAAAAAAAAAAAAAAAAQEAAAAAAAAAAAAAAAA' +
'AAAAAEQEAAAAAAAAAAAAAAAAAAAAA/9oADAMBAAIRAxEAPwA/8H//2Q==';
const img = new Image();
img.onload = () => {
const automatic = (img.width === 1 && img.height === 2);
_browser_quirks['image-orientation-automatic'] = automatic;
resolve(automatic ? 1 : orientation);
};
img.onerror = () => {
_browser_quirks['image-orientation-automatic'] = false;
resolve(orientation);
};
img.src = testImageURL;
}
});
// Some browsers don't allow reading from a canvas and instead return all-white
// or randomized data. Use a pre-defined image to check if reading the canvas
// works.
const checkCanvasReliability = () => new Promise((resolve, reject) => {
switch(_browser_quirks['canvas-read-unreliable']) {
case true:
reject('Canvas reading unreliable');
break;
case false:
resolve();
break;
default:
// 2×2 GIF with white, red, green and blue pixels
const testImageURL =
'data:image/gif;base64,R0lGODdhAgACAKEDAAAA//8AAAD/AP///ywAAAAAAgACAAACA1wEBQA7';
const refData =
[255, 255, 255, 255, 255, 0, 0, 255, 0, 255, 0, 255, 0, 0, 255, 255];
const img = new Image();
img.onload = () => {
const canvas = document.createElement('canvas');
const context = canvas.getContext('2d');
context.drawImage(img, 0, 0, 2, 2);
const imageData = context.getImageData(0, 0, 2, 2);
if (imageData.data.every((x, i) => refData[i] === x)) {
_browser_quirks['canvas-read-unreliable'] = false;
resolve();
} else {
_browser_quirks['canvas-read-unreliable'] = true;
reject('Canvas reading unreliable');
}
};
img.onerror = () => {
_browser_quirks['canvas-read-unreliable'] = true;
reject('Failed to load test image');
};
img.src = testImageURL;
}
});
const getImageUrl = inputFile => new Promise((resolve, reject) => {
if (window.URL && URL.createObjectURL) {
try {
resolve(URL.createObjectURL(inputFile));
} catch (error) {
reject(error);
}
return;
}
const reader = new FileReader();
reader.onerror = (...args) => reject(...args);
reader.onload = ({ target }) => resolve(target.result);
reader.readAsDataURL(inputFile);
});
const loadImage = inputFile => new Promise((resolve, reject) => {
getImageUrl(inputFile).then(url => {
const img = new Image();
img.onerror = (...args) => reject(...args);
img.onload = () => resolve(img);
img.src = url;
}).catch(reject);
});
const getOrientation = (img, type = 'image/png') => new Promise(resolve => {
if (!['image/jpeg', 'image/webp'].includes(type)) {
resolve(1);
return;
}
EXIF.getData(img, () => {
const orientation = EXIF.getTag(img, 'Orientation');
if (orientation !== 1) {
dropOrientationIfNeeded(orientation).then(resolve).catch(() => resolve(orientation));
} else {
resolve(orientation);
}
});
});
const processImage = (img, { width, height, orientation, type = 'image/png' }) => new Promise(resolve => {
const canvas = document.createElement('canvas');
if (4 < orientation && orientation < 9) {
canvas.width = height;
canvas.height = width;
} else {
canvas.width = width;
canvas.height = height;
}
const context = canvas.getContext('2d');
switch (orientation) {
case 2: context.transform(-1, 0, 0, 1, width, 0); break;
case 3: context.transform(-1, 0, 0, -1, width, height); break;
case 4: context.transform(1, 0, 0, -1, 0, height); break;
case 5: context.transform(0, 1, 1, 0, 0, 0); break;
case 6: context.transform(0, 1, -1, 0, height, 0); break;
case 7: context.transform(0, -1, -1, 0, height, width); break;
case 8: context.transform(0, -1, 1, 0, 0, width); break;
}
context.drawImage(img, 0, 0, width, height);
canvas.toBlob(resolve, type);
});
const resizeImage = (img, type = 'image/png') => new Promise((resolve, reject) => {
const { width, height } = img;
const newWidth = Math.round(Math.sqrt(MAX_IMAGE_PIXELS * (width / height)));
const newHeight = Math.round(Math.sqrt(MAX_IMAGE_PIXELS * (height / width)));
checkCanvasReliability()
.then(getOrientation(img, type))
.then(orientation => processImage(img, {
width: newWidth,
height: newHeight,
orientation,
type,
}))
.then(resolve)
.catch(reject);
});
export default inputFile => new Promise((resolve) => {
if (!inputFile.type.match(/image.*/) || inputFile.type === 'image/gif') {
resolve(inputFile);
return;
}
loadImage(inputFile).then(img => {
if (img.width * img.height < MAX_IMAGE_PIXELS) {
resolve(inputFile);
return;
}
resizeImage(img, inputFile.type)
.then(resolve)
.catch(() => resolve(inputFile));
}).catch(() => resolve(inputFile));
});
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