Vue progressive image loading plugin
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Latest commit 57d59ad Jul 16, 2018

README.md

vue-progressive-image

Vue progressive image loading plugin

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Installation

$ npm install vue-progressive-image

Usage

import Vue from 'vue'
import VueProgressiveImage from 'vue-progressive-image'

Vue.use(VueProgressiveImage)

Progressive image

Instead of using the normal img tag to load images

<img src="https://unsplash.it/1920/1080?image=10" />

use the progressive-img component already globally available after the plugin installation

<progressive-img src="https://unsplash.it/1920/1080?image=10" />

Progressive background

It is also possible to apply progressive images as backgrounds and it will have the same props as the progressive-img component

<progressive-background src="https://unsplash.it/1920/1080?image=10" />

Placeholders

To be able to immediately show some feedback to the user, it is possible to pass a placeholder image, which could be also 1% the size of the main image: it will be blurred so you can go crazy with optimizations here.

in this example I actually use the same image, but you have the idea here

<progressive-img
  src="https://unsplash.it/1920/1080?image=10"
  placeholder="https://unsplash.it/1920/1080?image=10"
/>

The slot (progressive-background only)

The progressive-background has a "content" slot, which can hold content that needs to be rendered over the background image and also can hold a preloader. This slot has one property called "visible" that tells you when, for example, a preloader needs to be visible or not.

<progressive-background src="https://unsplash.it/1920/1080?image=10">
  <div slot="content" slot-scope="{ visible }">
    <p>I am some content to display over the image</p>
    <div v-show="visible">I am the preloader</div>
  </div>
</progressive-background>

Blur

It is possible to adjust the level of blur applied to the placeholder image

<progressive-img
  src="https://unsplash.it/1920/1080?image=10"
  placeholder="https://unsplash.it/1920/1080?image=10"
  :blur="30"
/>

Ratio

It is possible to remove the padding that adds the aspect ratio to the container.

<progressive-img
  src="https://unsplash.it/1920/1080?image=10"
  no-ratio
/>

It is also possible to manually specify the image aspact ratio when you know it. It allows the placeholder to be displayed in the correct aspect ratio. The ratio is calculated as height / width.

<progressive-img
  src="https://unsplash.it/1920/1080?image=10"
  aspect-ratio="1.5"
/>

Image fallback

In case of a loading error of the main image, it is possible to add a fallback image which can display an error image or just another image.

<progressive-img
  src="https://this_url_should_cause_an_error"
  fallback="https://unsplash.it/1920/1080?image=10"
/>

Events

Each component emits an event whenever an image is loaded.

Because we usually load two images, a main image and a placeholder, two events are dispatched onLoad and onLoadPlaceholder

in your js file

export default {
  methods: {
    onLoad () {
      // main image is loaded
    },
    onLoadPlaceholder () {
      // placeholder image is loaded
    },
    onError (error) {
      // main image error
    },
    onErrorPlaceholder (error) {
      // placeholder image error
    }
  }
}

in the html just add the events you need to listen to

<progressive-img
  @onLoad="onLoad"
  @onLoadPlaceholder="onLoadPlaceholder"
  @onError="onError"
  @onErrorPlaceholder="onErrorPlaceholder"
  src="https://unsplash.it/1920/1080?image=10"
  placeholder="https://unsplash.it/1920/1080?image=10"
/>

Options

During the installation process it is possible to pass some default global options

Cached images

  • type: Boolean
  • default: true

Cached images are checked by default. This check kills the animation if the image was already loaded once. If you would like to show the animation every time, even when is not needed, you can simply use the plugin options like so:

Vue.use(VueProgressiveImage, {
  cache: false
})

placeholder

  • type: String
  • required: false
Vue.use(VueProgressiveImage, {
  placeholder: 'https://unsplash.it/1920/1080?image=20'
})

blur

  • type: Number
  • required: false
  • default: 5
Vue.use(VueProgressiveImage, {
  blur: 30
})

delay

  • type: Number
  • default: 0

This options is for debug only. It lets you have an easy look at the placeholder before the main image is fully loaded.

Vue.use(VueProgressiveImage, {
  delay: 2000 // 2 seconds before the image is displayed
})

Global options like placeholder and blur will be applied only to components that don't specify their own options

Examples

Check out the example folder in the root of the repository for a small vue page with some examples on how to use the plugin. If you want to add some new example, just make a PR and I will add them :)

Issues and features requests

Please drop an issue, if you find something that doesn't work, or a feature request at https://github.com/MatteoGabriele/vue-progressive-image/issues

Follow me on twitter @matteo_gabriele