README

Tachyon is an image resizing service built to be used with Amazon S3 as the image backend, AWS Lambda (or any node.js server) to process images using sharp, and sits behind a CDN such as CloudFront or CloudFlare.

This plugin handles modifying WordPress image URLs to use a Tachyon service instance.

Installation

1. Upload and enable this plugin.
2. Add define( 'TACHYON_URL', 'https://your.tachyon.url/path/to/uploads' ) to your wp-config.php file.

Usage

Typically the above steps are all you need to do however you can use the following public facing functions and filters.

Functions

tachyon_url( string $image_url, array $args = [] )

This function returns the Tachyon URL for a given image hosted on Amazon S3.

$image_url = 'https://my-bucket.s3.us-east-1.amazonaws.com/path/to/image.jpg';
$args      = [
	'resize'  => '300,300',
	'quality' => 90
];

$url = tachyon_url( $image_url, $args );

Filters

The following filters allow you to modify the output and behaviour of the plugin.

tachyon_disable_in_admin

Defaults to true. You can override this by adding the following code to a plugin or your theme's functions.php:

add_filter( 'tachyon_disable_in_admin', '__return_false' );

tachyon_override_image_downsize

Defaults to false. Provides a way of preventing Tachyon from being applied to images retrieved from WordPress Core at the lowest level, you might use this if you wanted to use tachyon_url() manually in specific cases.

add_filter( 'tachyon_override_image_downsize', '__return_true' );

tachyon_skip_for_url

Allows skipping the Tachyon URL for a given image URL. Defaults to false.

add_filter( 'tachyon_skip_for_url', function ( $skip, $image_url, $args ) {
	if ( strpos( $image_url, 'original' ) !== false ) {
		return true;
	}
	
	return $skip;
}, 10, 3 );

tachyon_pre_image_url

Filters the Tachyon image URL excluding the query string arguments. You might use this to shard Tachyon requests across multiple instances of the service for example.

add_filter( 'tachyon_pre_image_url', function ( $image_url, $args ) {
	if ( rand( 1, 2 ) === 2 ) {
		$image_url = str_replace( TACHYON_URL, TACHYON_URL_2, $image_url );
	}
	
	return $image_url;
}, 10, 2 );

tachyon_pre_args

Filters the query string parameters appended to the tachyon image URL.

add_filter( 'tachyon_pre_args', function ( $args ) {
	if ( isset( $args['resize'] ) ) {
		$args['crop_strategy'] = 'smart';
	}
	
	return $args;
} );

tachyon_remove_size_attributes

Defaults to true. width & height attributes on image tags are removed by default to prevent aspect ratio distortion that can happen in some unusual cases where srcset sizes have different aspect ratios.

add_filter( 'tachyon_remove_size_attributes', '__return_true' );

Credits

Created by Human Made for high volume and large-scale sites, such as Happytables. We run Tachyon on sites with millions of monthly page views, and thousands of sites.

Written and maintained by Joe Hoyle.

Tachyon is forked from Photon by Automattic Inc. As Tachyon is not an all-purpose image resizer, rather it uses a media library in Amazon S3, it has a different use case to Photon.

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