diff options
Diffstat (limited to 'app/javascript/flavours/glitch/util/resize_image.js')
-rw-r--r-- | app/javascript/flavours/glitch/util/resize_image.js | 189 |
1 files changed, 189 insertions, 0 deletions
diff --git a/app/javascript/flavours/glitch/util/resize_image.js b/app/javascript/flavours/glitch/util/resize_image.js new file mode 100644 index 000000000..fb8c3c11e --- /dev/null +++ b/app/javascript/flavours/glitch/util/resize_image.js @@ -0,0 +1,189 @@ +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)); +}); |