Posthtml-webp NPM

posthtml-webp

This plugin add webp supporting in your html. Also supports <amp-img>

Install

$ npm i posthtml posthtml-webp

Usage

const fs = require('fs');
const posthtml = require('posthtml');
const posthtmlWebp = require('posthtml-webp');

posthtml()
    .use(posthtmlWebp(/* Plugin options */))
    .process(html/*, options */)
    .then(result => fs.writeFileSync('./after.html', result.html));

Example

Before:

<img src="image.jpg">
<amp-img alt="photo" width="550" height="368" layout="responsive" src="photo.png"></amp-img>

After:

<picture>
    <source type="image/webp" srcset="image.jpg.webp">
    <img src="image.jpg">
</picture>
<amp-img alt="photo" width="550" height="368" layout="responsive" src="photo.png.webp">
    <amp-img alt="photo" width="550" height="368" layout="responsive" src="photo.png" fallback=""></amp-img>
</amp-img>

Options

`extension`

Type: string Default: .webp Description: Add custom extension or even prefix Example: image.jpg => image.jpg?as=webp (instead of image.jpg.webp)

`replaceExtension`

Type: Boolean Default: false Description: Replace the extension of the source image with .webp instead of appending .webp to the original filename Example: image.jpg => image.webp (instead of image.jpg.webp)

`classIgnore`

Type: Array<string> Default: [] Description: list of classes for which the transformation will be ignored Example: classIgnore: ['ignore-webp'] will ignore transformation for images with the class ignore-web

`extensionIgnore`

Type: Array<string> Default: [] Description: list of extension for which the transformation will be ignored Example: extensionIgnore: ['svg'] will ignore transformation for images with the svg extension

`lazySrcset`

Type: String Default: data-srcset Description: The attribute used for lazy webp loading. Use it if you have lazy attribute for srcset on your images. It will be set on created <source> to later be processed by external lazy loading library. Example: lazySrcset: 'my-srcset' will set my-srcset attribute on <source>

`lazySrc`

Type: String Default: data-src Description: The attribute used for lazy webp loading. The original <img> may not contain src at all, but instead some custom lazy-loading attribute. Or it may contain just a placeholder image inside src which shouldn't be used for webp conversion. lazySrc will define a custom attribute name to look at when processing your lazy loaded images. Note that lazySrcset is still needed even if <img> has only lazySrc defined, because srcset is the mechanism for defining a source file for the <source>. See lazySrcset option description. Example: lazySrc: 'my-src' will convert an image inside my-src attribute, instead of regular src.