johnnylee-dev/v-lazy-image

Lazy load images using Intersection Observer, apply progressive rendering and css animations.

v-lazy-image

A Vue.js component to lazy load an image automatically when it enters the viewport using the Intersection Observer API.

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Demos

• Simple demo
• Responsive images, by @aarongarciah
• Progressive image loading with animations, by @aarongarciah
• Performant progressive blur using SVG

Usage

npm install v-lazy-image

Warning: You'll need to install the w3c Intersection Observer polyfill in case you're targeting a browser which doesn't support it.

You can register the component globally so it's available in all your apps:

import Vue from "vue";
import { VLazyImagePlugin } from "v-lazy-image";

Vue.use(VLazyImagePlugin);

Or use it locally in any of your components:

import VLazyImage from "v-lazy-image";

export default {
  components: {
    VLazyImage
  }
};

You must pass an src property with the link of the image:

<template>
  <v-lazy-image src="http://lorempixel.com/400/200/" />
</template>

That image will be loaded as soon as the image enters the viewport.

Progressive Loading

You can use the src-placeholder property to define an image that is shown until the src image is loaded.

When the src image is loaded, a v-lazy-image-loaded class is added, so you can use it to perform animations. For example, a blur effect:

<template>
  <v-lazy-image
    src="https://cdn-images-1.medium.com/max/1600/1*xjGrvQSXvj72W4zD6IWzfg.jpeg"
    src-placeholder="https://cdn-images-1.medium.com/max/80/1*xjGrvQSXvj72W4zD6IWzfg.jpeg"
  />
</template>

<style scoped>
.v-lazy-image {
  filter: blur(10px);
  transition: filter 0.7s;
}
.v-lazy-image-loaded {
  filter: blur(0);
}
</style>

In case you are using Webpack bundler for images too (just like Vue-cli):

<v-lazy-image
  src="https://cdn-images-1.medium.com/max/1600/1*xjGrvQSXvj72W4zD6IWzfg.jpeg"
  :src-placeholder="require('../assets/img.jpg')"
/>

You could listen to the intersect and load events for more complex animations and state handling:

<template>
  <v-lazy-image
    src="https://cdn-images-1.medium.com/max/1600/1*xjGrvQSXvj72W4zD6IWzfg.jpeg"
    src-placeholder="https://cdn-images-1.medium.com/max/80/1*xjGrvQSXvj72W4zD6IWzfg.jpeg"
    @intersect="..."
    @load="..."
  />
</template>

@jmperezperez has written about the progressive loading technique on his blog, in case you want a deeper explanation.

Responsive Images

Using the srcset property you can set images for different resolutions:

<template>
  <v-lazy-image
    srcset="image.jpg 1x, image_2x.jpg 2x"
  />
</template>

When using the srcset attribute is recommended to use also src as a fallback for browsers that don't support the srcset and sizes attributes:

<template>
  <v-lazy-image
    srcset="image-320w.jpg 320w, image-480w.jpg 480w"
    sizes="(max-width: 320px) 280px, 440px"
    src="image-480w.jpg"
  />
</template>

The srcset prop is combinable with src-placeholder in order to apply progressive loading.

Picture

If you want to wrap the img in a picture tag, use the prop usePicture. You can then use slots to add additional elements above the img element`.

<v-lazy-image
  srcset="image-320w.jpg 320w, image-480w.jpg 480w"
  alt="Fallback"
  use-picture
>
  <source srcset="image-320w.jpg 320w, image-480w.jpg 480w" />
</v-lazy-image>

Renders as:

<picture>
  <source srcset="image-320w.jpg 320w, image-480w.jpg 480w" />
  <img srcset="image-320w.jpg 320w, image-480w.jpg 480w" alt="Fallback" />
</picture>

Note you can use the picture polyfill.

API

Aside from the following API, you can pass any img attribute, such as alt, and they'll be added to the rendered <img> tag.

Fields marked as (*) are required.

Props

Name	Type	Default	Description
src	String (*)	-	Image src to lazy load when it intersects with the viewport
src-placeholder	String	' '	If defined, it will be shown until the src image is loaded. Useful for progressive image loading, see demo
srcset	String	-	Images to be used for different resolutions
intersection-options	Object	() => ({})	The Intersection Observer options object.
use-picture	Boolean	false	Wrap the img in a picture tag.

Events

Name	Description
intersect	Triggered when the image intersects the viewport
load	Triggered when the lazy image defined in src is loaded