/
image-resizer.js
94 lines (75 loc) · 2.61 KB
/
image-resizer.js
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/*
Private API
*/
async function getImageElement(imageSource) {
return await new Promise((resolve, reject) => {
const image = new Image();
image.onload = () => resolve(image);
image.onerror = () => reject({ reason: 'getImageElement: Image Load Error' });
image.src = imageSource;
})
}
async function getMime(imageSource) {
const image = await fetch(imageSource);
return (await image.blob()).type;
};
function getResizedDimensions(elem, maxDimensionSize) {
// This code has high complexity, don't dwell on it too much
// I wrote it like this to keep what really matters more simplified
const
[ bigSide, smallSide ] = elem.width > elem.height ?
['width', 'height']:
['height', 'width'];
// if big side is smaller than our max dimension, then pass dimensions through
if(maxDimensionSize > elem[bigSide] || !maxDimensionSize){
return {
[bigSide]: elem[bigSide],
[smallSide]: elem[smallSide]
}
}
return {
[bigSide]: maxDimensionSize,
[smallSide]: maxDimensionSize / elem[bigSide] * elem[smallSide]
}
}
function createCanvasImage(imageElement, dimensions) {
const canvas = document.createElement("canvas");
const ctx = canvas.getContext('2d');
canvas.width = dimensions.width;
canvas.height = dimensions.height;
ctx.drawImage(imageElement, 0, 0, dimensions.width, dimensions.height);
return canvas;
}
/*
Public API
*/
export async function loadFile(file) {
console.log(file)
return await new Promise((resolve, reject) => {
const fileReader = new FileReader();
fileReader.onload = (e) => resolve(e.target.result);
fileReader.onabort = () => reject({ reason: 'loadFile: File Read Aborted' });
fileReader.onerror = () => reject({ reason: 'loadFile: File Read Error' });
fileReader.readAsDataURL(file);
});
}
export async function resizeImage(imageSource, maxDimensionSize) {
const mime = await getMime(imageSource);
const imageElement = await getImageElement(imageSource);
const dimensions = getResizedDimensions(imageElement, maxDimensionSize);
const image = createCanvasImage(imageElement, dimensions);
return {
blob: await new Promise((resolve) => {
image.toBlob(blob => resolve(blob), mime, 1);
}),
dataURL: image.toDataURL(mime, 1)
}
}
export async function getResizedImageFromFile(file, maxDimensionSize) {
return await new Promise(async (resolve, reject) => {
const imageSource = await loadFile(file).catch((e) => reject(e));
const resizedImage = await resizeImage(imageSource, maxDimensionSize).catch(((e) => reject(e)));
resolve(resizedImage);
});
}
export default getResizedImageFromFile;