chinwagsocial/app/javascript/mastodon/utils/resize_image.js
Yamagishi Kazutoshi 0758b00bfd Refactor resizeImage method (#7236)
- Use URL.createObjectURL (replace from FileReader)
- Use HTMLCanvasElement.prototype.toBlob
  (replace from HTMLCanvasElement.prototype.toDataURL)
- Use Promise (replace callback interface)
2018-04-23 09:15:51 +02:00

66 lines
1.7 KiB
JavaScript

const MAX_IMAGE_DIMENSION = 1280;
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);
});
export default inputFile => new Promise((resolve, reject) => {
if (!inputFile.type.match(/image.*/) || inputFile.type === 'image/gif') {
resolve(inputFile);
return;
}
loadImage(inputFile).then(img => {
const canvas = document.createElement('canvas');
const { width, height } = img;
let newWidth, newHeight;
if (width < MAX_IMAGE_DIMENSION && height < MAX_IMAGE_DIMENSION) {
resolve(inputFile);
return;
}
if (width > height) {
newHeight = height * MAX_IMAGE_DIMENSION / width;
newWidth = MAX_IMAGE_DIMENSION;
} else if (height > width) {
newWidth = width * MAX_IMAGE_DIMENSION / height;
newHeight = MAX_IMAGE_DIMENSION;
} else {
newWidth = MAX_IMAGE_DIMENSION;
newHeight = MAX_IMAGE_DIMENSION;
}
canvas.width = newWidth;
canvas.height = newHeight;
canvas.getContext('2d').drawImage(img, 0, 0, newWidth, newHeight);
canvas.toBlob(resolve, inputFile.type);
}).catch(reject);
});