@morr/image-promise

image-promise

Load one or more images, return a promise. Only 0.5KB, for the browser, no dependencies.

It can be used in two ways:

• pass a URL: it will generate an <img> and wait for it to load:

  loadImage('img.jpg').then(/* It's loaded! */)
  

• pass an <img>: it will wait for it to load:

  const img = document.querySelector('img.my-image');
  loadImage(img).then(/* It's loaded! */)
  

• pass an array of URLs and/or <img>s, wait for them to load:

  const img = document.querySelector('img.my-image');
  loadImage([img, 'loading.gif']).then(/* Both are loaded! */)
  

Install

You can download the standalone bundle

Or use npm:

npm install image-promise

// This module is only offered as a ES Module
import loadImage from 'image-promise';

Usage

One image

loadImage(image) will return a Promise that resolves when the image load, or fails when the image

const image = 'cat.jpg';
// const image = $('img')[0]; // it can also be an <img> element

loadImage(image)
.then(function (img) {
	ctx.drawImage(img, 0, 0, 10, 10);
})
.catch(function () {
	console.error('Image failed to load :(');
});

Multiple images

image-promise can load multiple images at a time

const images = ['cat.jpg', 'dog.jpg'];
// const images = $('img'); // it can also be a jQuery object
// const images = document.querySelectorAll('img'); // or a NodeList

loadImage(images)
.then(function (allImgs) {
	console.log(allImgs.length, 'images loaded!', allImgs);
})
.catch(function (err) {
	console.error('One or more images have failed to load :(');
	console.error(err.errored);
	console.info('But these loaded fine:');
	console.info(err.loaded);
});

Set custom attributes

loadImage(image, attributes) lets you pass as the second argument an object of attributes you want to assign to the image element before it starts loading.

This is useful for example when you need CORS enabled image, where you need to set the attribute crossorigin="anonymous" before the image starts downloading.

const image = 'https://catpics.com/cat.jpg';

loadImage(image, { crossorigin: 'anonymous' })
.then(function (img) {
	ctx.drawImage(img, 0, 0, 10, 10);

	// now you can do this
	canvas.toDataURL('image/png')
})
.catch(function () {
	console.error('Image failed to load :(');
});

Dependencies

None! But you need to polyfill window.Promise in IE11 and lower.

License

MIT © Federico Brigante