Uses picture sets generated by metalsmith-picset-generate to give browsers choice

Example use

Add to your pipeline like

npm i metalsmith-picset-handlebars-helper --save

const picsetHandlearsHelper = require('metalsmith-picset-handlebars-helper')
Metalsmith(__dirname)
	...
	.use(picsetHandlearsHelper())
	...

Assume

• You have a handlebars package installed somewhere either directly or as a sub-dependency (We use that same version / install)
• /img/picset/anthony_80webp_90jpg_2000,1000,500w.jpg as a 2000px wide 90% quality photo
• metalsmith-picset-generate is used earlier in your metalsmith pipeline

Then use the handlebars helper like {{{picset "anthony" 500}}} to output something like

<picture>
	<source type="image/webp"
		srcset="img/srcsets/anthony-2000.webp 2000w, img/srcsets/anthony-1000.webp 1000w, img/srcsets/anthony-500.webp 500w" sizes="100vw" />
	<img src="img/srcsets/anthony-500.jpg"
		srcset="img/srcsets/anthony-2000.jpg 2000w, img/srcsets/anthony-1000.jpg 1000w, img/srcsets/anthony-500.jpg 500w" sizes="100vw" />
</picture>

Specification

Metalsmith requirements

• You have a handlebars package installed somewhere either directly or as a sub-dependency (We use that same version / install)

Metalsmith options object

{
	path: 'img/picset'
}

path

• Relative to Metalsmith source folder
• Default: img/picset/

Helper use

Like {{{picset NAME DEFAULT_WIDTH SIZES ALT}}}

• Parameter 1 (NAME): Image source name
• Parameter 2 (DEFAULT_WIDTH): Default width
• Parameter 3 (SIZES): Optional sizes
• Parameter 4 (ALT): Optional alt tag

Generates <picture> elements with:

• srcset parameters that include all files found following metalsmith-picset-generate's naming convention
• <source> with .webp type in srcset
• <img> with:
• srcset with file type of .jpg, .png, or .svg as a fallback
• src at default width and same file type as it's srcset
• sizes attribute as specified duplicated on both the <source> and <img ...> tags

Background info

Philosophy

• Convention over Configuration
• Simple case of resizing only (artistic decisions not thought through for this)
• Give the browser all availble choices
• Reduce bandwidth bloat and keep high quality:

1. .webp is first choice
2. Responsive size is first choice
3. Always give fallbacks

• Standards based (Using <picture> with inner <img src="..."> fallback)

Inspiration

• Responsive Images: If you’re just changing resolutions, use srcset
• Don’t use <picture> (most of the time)
• Using the picture element to load WebP images with fallback
• Srcset and sizes

Implementation

• Implemented on Node v6.9.1, untested in other versions
• Doesn't install handlebars, as assumes you have it in your MetalSmith install and we want to use that same version