hometown/app/javascript/mastodon/utils/resize_image.js
ThibG be637146f3
Fix uninformative error message when uploading unsupported image files (#13540)
Attempting to upload image files that the browser is unable to load results
in “Oops! An unexpected error occurred.”

This commit changes the error handling so that an unprocessable image results
in the file being sent anyway, which might cover a few corner cases, and
provide a slightly better error message.
2020-04-25 12:27:29 +02:00

158 lines
4.9 KiB
JavaScript

import EXIF from 'exif-js';
const MAX_IMAGE_PIXELS = 1638400; // 1280x1280px
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;
}
});
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 (type !== 'image/jpeg') {
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);
// The Tor Browser and maybe other browsers may prevent reading from canvas
// and return an all-white image instead. Assume reading failed if the resized
// image is perfectly white.
const imageData = context.getImageData(0, 0, width, height);
if (imageData.data.every(value => value === 255)) {
throw 'Failed to read from canvas';
}
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)));
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));
});