README

A plugin which provides dynamic image sizes through a CDN

Requirements

A resizer service, this plugin currently supports:

• A cloudflare CDN zone with image resizing enabled.
• KeyCDN with pull zone configured
• Fastly with image optimzer enabled

Note that you'll need to manage the loading attribute yourself. Only tags with loading="lazy" will get rewritten to use lozad.js. You should ensure that the LCP blocks have loading="eager" or no loading attribute at all.

IMAGERESIZER_ZONE environment variable is required.

Environment variables

IMAGERESIZER_ZONE='https://myapp.com/cdn-cgi/image/'
IMAGERESIZER_DISABLED=false

Features

• Use lozad.js to lazyload images, iframes and videos
• Support for sizes="auto" through data-sizes="auto", which is resolved against the element's rendered box. For images using object-fit: cover or object-fit: contain the painted image can be larger than its box, so the intrinsic aspect ratio is taken into account to avoid requesting a too-small, blurry candidate.
• Preload first blocks image
• Rewrite image URLs to use Cloudflare CDN
• Replace all WP srcset with our Cloudflare Image Resizing URLs

API

See Cloudflare docs, KeyCDN docs or Fastly docs for transformation options.

Pass custom options

You can pass custom options to the resizer when using wp_get_attachment_image by setting data-resizer-args which supportes wp_parse_args type strings.

wp_get_attachment_image($profileImage, 'full', false, [
  'data-resizer-args' => 'crop=1:1&quality=50',
  'sizes' => '(min-width: 40em) 48px, (min-width: 68.75em) 56px, (min-width: 87.5em) 64px, 40px'
])

Generate src and srcset from URL

use GeneroWP\ImageResizer\Image;

$image = new Image($url, [
    'blur' => 50,
]);

return sprintf(
    '<img loading="eager" class="wp-block-cover__image-background" src="%s" srcset="%s" sizes="%s">',
    $image->src(),
    $image->srcset(),
    '100vw'
);

Generate src and srcset from attachment

use GeneroWP\ImageResizer\Image;

$image = Image::fromAttachment($bannerImageId, 'full', [
    'fit' => 'cover',
    'height' => 350 * 2,
]);

return sprintf(
    '<img loading="eager" class="wp-block-cover__image-background" src="%s" srcset="%s" sizes="%s">',
    $image->src(),
    $image->srcset(),
    '100vw'
);

Add a preload link tag to head

use GeneroWP\ImageResizer\Rewriters\Preload;

add_action('wp_head', function () {
    if (is_singular('recipe')) {
        $composer = new ContentRecipe();
        $featured = $composer->featuredImageHtml(get_post());
        echo Preload::buildLink($featured);
    }
}, 2);

Filters

// Alter rewriters
add_filter('wp-image-resizer/rewriters', function (array $rewriters) {
    $rewriters[] = MyCustomRewriter::class;
    return $rewriters;
});

// Alter resizer URLs
add_filter('wp-image-resizer/image/url', function (string $url) {
    if (defined('WP_ENV') && WP_ENV === 'development') {
        $url = str_replace('development-domain.ddev.site', 'production-domain.com', $url);
    }
    return $url;
});

// Alter blocks that should be considered for preloading
add_filter('wp-image-resizer/preload/blocks', function (array $blockTypes) {
    $blockTypes[] = 'my-theme/hero-banner';
    return $blockTypes;
});

// Alter if preload should stop iterating blocks
add_filter('wp-image-resizer/preload/should_stop', function (bool $stop, array $block, array $blocks) {
    if ($block['blockType'] === 'my-theme/breadcrumb') {
        return false;
    }
    return $stop;
}, 10, 3);

// Alter srcset breakpoints
add_filter('wp-image-resizer/config/breakpoints', function (array $breakpoints) {
    return [
        ...range(50, 500, 50),
        ...range(600, 2000, 100),
    ];
});

// Alter default resizing settings
add_filter('wp-image-resizer/config/default', function (array $breakpoints) {
    return [
        'quality' => 90
    ];
});

Development

Install dependencies

composer install
npm install

Run the tests

npm run test

Build assets

# Minified assets which are to be committed to git
npm run build:production

# Watch for changes and re-compile while developing the plugin
npm run start