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ResponsivePics

ResponsivePics is a WordPress plugin that enables WordPress theme authors to automatically resize images^* in responsive layouts.

• Saves bandwidth and lets your site load faster
• No need anymore for defining custom image sizes
• Adds retina support to your theme images
• Supports art-directed responsive images
• Supports image srcset & sizes attributes
• Supports focal point based crops
• Supports aspect ratio based crops
• Supports WebP images (requires Wordpress 5.8 or higher)
• Supports LQIP (low quality image placeholder)
• Supports lazyloading
• Supports intrinsic ratio boxes
• Supports offloading media to S3 storage with WP Offload Media (Lite)
• Supports WP REST API
• Uses background processing for resize- and crop tasks

_{^{*ReponsivePics does not handle images in the WordPress wysiwig editor, it’s only useful for theme authors that use images or photos in their themes. It automatically handles retina or hdpi images via media queries.}}

Documentation

For full documentation and examples visit: responsive.pics

Table of contents

1. Requirements
2. Installation
3. Configuration
4. Usage
5. Sizes
6. Cropping
7. Process
8. Hooks
9. Features

Requirements

Installation

You can install this plugin via the command-line or the WordPress admin panel.

via Command-line

If you're using Composer to manage WordPress, add ResponsivePics to your project's dependencies.

Then activate the plugin via wp-cli.

via WordPress Admin Panel

1. Download the latest zip of this repo.
2. In your WordPress admin panel, navigate to Plugins->Add New
3. Click Upload Plugin
4. Upload the zip file that you downloaded.
5. Activate the plugin after installation.

Browser Support

Currently the <picture> element and srcset and sizes attributes on the <img> element are supported in all modern browsers except Internet Explorer 11.

In order to enable support for the picture element and associated features in browsers that do not yet support them, you can use a polyfill. We recommend using Picturefill.

To install Picturefill in your wordpress theme as a node module, run the following command from your theme directory:

npm

npm install --save picturefill

Yarn

yarn add picturefill

And import the package in your theme’s global javascript file: import 'picturefill';

Configuration

ResponsivePics uses the following default variables:

By default, ResponsivePics will use the Bootstrap 4 SCSS variables for defining:

The amount of grid columns: $grid-columns: 12;
The grid gutter width in pixels: $grid-gutter-width: 30px;
The grid breakpoints in pixels:

And the maximum widths of the containers in pixels:

Note: ResponsivePics will add the xs container max width for you (= 576), based upon the default sm grid breakpoint (= 576px).

If you have customized the bootstrap defaults or if you’re using a different grid system (Foundation, Materialize etc.), or even if you want to add extra breakpoints & container widths, you can pass your own grid variables to the ResponsivePics library.

Add these lines to your theme’s functions.php and make sure to check if the ResponsivePics class exists:

Helper Functions

You can retrieve any variables used in ResponsivePics by running one of these helper functions:

Usage

Image Element

For inserting a responsive <img> element in your template, use the get_image function or the responsive-pics/v1/image API endpoint with the available parameters.

PHP

REST API

Image Parameters

Image Data

For retrieving the responsive <img> data in your theme, you can use the get_image_data function or the responsive-pics/v1/image-data API endpoint with the available parameters id, sizes, crop, classes, lazyload and lqip.

PHP

REST API

This will return an array containing the available image sources per breakpoint, alt text, mime type, boolean values for alpha channel and lazyload, an url for the lqip image and an array for the css classes.

Picture Element

For inserting a responsive <picture> element in your template, use the get_picture function or the responsive-pics/v1/picture API endpoint with the available parameters.

PHP

REST API

Picture Parameters

Picture Data

For retrieving the responsive <picture> data in your theme, you can use the get_picture_data function or the responsive-pics/v1/picture-data API endpoint with the available parameters id, sizes, classes, lazyload and intrinsic.

PHP

REST API

This will return an array containing the available picture sources per breakpoint, alt text, mime type, boolean values for alpha channel and intrinsic, an array for the picture css classes and an array for the img css classes.

Background Image

For inserting a responsive background image in your template, use the get_background function or the responsive-pics/v1/background API endpoint with the available parameters.

PHP

REST API

Background Parameters

Background Data

For retrieving the responsive background image data in your theme, you can use the get_background_data function or the responsive-pics/v1/background-data API endpoint with the available parameters id, sizes and classes.

PHP

REST API

This will return an array containing the available background image sources per breakpoint, alt text, mime type, a boolean value if the image has an alpha channel, an id for the background and an array for the background css classes.

Supported image formats

The following image file formats are supported:

Any other image formats, will not be resizes or cropped.

Sizes

Image sizes

The following syntax is available for each image size in the sizes parameter:

Picture & background sizes

Since the <picture> element and background images support art directed images, the following full syntax is available for each image size in the sizes parameter:

The following parameters are available in the sizes syntax:

Cropping

The following options are available as valid crop positions:

Crop position shorthands

You can use the following crop position shorthands in horizontal direction (x):

• l: left
• c: center
• r: right
• f: focal point (See the Focal Point section for more information)

And in vertical direction (y):

• t: top
• c: center
• b: bottom

If the vertical direction is not set, the horizontal direction x will be treated as a shortcut:

• c: center center
• t: top center
• r: right center
• b: center bottom
• l: left center
• f: focal point (See the Focal Point section for more information)

Crop position percentages

You can also use percentages as valid crop position syntax:

• 75 10: 75% from left, 10% from top
• 25 80: 25% from left, 80% from top
• 50 100: 50% from left, 100% from top (equals center bottom)

In this case both the coordinates x and y need to be passed.

Focal Point

When you want to crop an image but keep a certain area of the image in view, you can use the f(ocal) shorthand feature. In order to set this focal area of an image, we added a focal point picker interface to several views of the Wordpress media framework.

Attachment Details

When clicking on a thumbnail from the Wordpress Media Library grid view, you will see the Attachment details modal. This will be the most accurate view to select your focal point:

Featured Image

When setting or replacing an featured image in a page or post, you will see the Featured image modal. In this view you can select your focal point in the thumbnail at the top of the right sidebar:

Edit Image

When uploading or editing an image in the WYSIWYG editor or meta field in a page or post, you will see the Edit image modal. In this view you can select your focal point in the thumbnail at the top left:

There are 3 ways you can set the focal point of an image with the interface:

• By directly clicking on the desired focal point in the image.
• By dragging and dropping the focal point circle element on the image.
• By entering the Focal Point X & Y-axis values as percentages directly in the attachment input fields.

By using one of these options a post meta key named responsive_pics_focal_point will be added or updated to the attachment with an array value containing the x & y coordinates as percentages:

To use this value elsewhere in your theme, you can retrieve it by calling:

Process

1. When visiting a front-end page and a ResponsivePics function call is made, this library will add the resize and/or crop image task as a job to the background process queue using Action Scheduler.
2. On every page load or on the next cron interval, Action Scheduler will run the next batch of jobs in the background process queue. See the Cron section for more information.
3. When a job is up next in the queue and ready to be processed it will execute the resize and/or crop task and save the image in the same location as the original image when successful and it will remove the job from the queue.
4. Once the image variation is created, it will skip the process of that variation on the next page load.
5. When you change one of the image size parameters, it will automatically try and create the new image variation on the next page load.
6. When the original image does not meet the dimension requirements of the requested image size, it will skip that image size variation and proceed to the next image size.
7. Alt text will automatically be added on the picture img element if the original image in the media library has one.
8. When deleting an attachment from the library, it will also delete all the resized images created by this plugin.

Background Processing

The background processing library Action Scheduler has a built in administration screen for monitoring, debugging and manually triggering scheduled image resize jobs. The administration interface is accesible via:

Every resize job will be grouped by it's wordpress image id

Cron

When you are using the built-in WP-Cron, the background process queue will only process any tasks on every page load.
If you have disabled WP-Cron in your setup and you are using your own cron job on your server, Action Scheduler will use the interval set in that cron job to process the next batch of jobs.

If you're using Trellis like us ❤️, the default cron interval is set to every 15 mins.
You can override this to for example 1 mins with setting the cron_interval (or cron_interval_multisite for multisite) variable per wordpress site to */1:

In for example trellis/group_vars/development/wordpress_sites.yml:

Don't forget to re-provision your server after changing this value.

Error handling

If an error occurs during the resizing process or if there's invalid syntax, ResponsivePics will display or return an error.

PHP

ResponsivePics errors
- breakpoint xxs is neither defined nor a number

REST API

Hooks

The following actions allow you to hook into the image resizing process timeline. You can place them in your theme's functions.php file.

responsive_pics_request_scheduled

This action fires when ResponsivePics has scheduled a new image resize request to the ActionScheduler queue.

Parameters

• $post_id
  (integer) The attachment ID

• $resize_request
  (array) The resize request parameters:

responsive_pics_request_processed

This action fires when the ActionScheduler has processed an image resize request in the queue.

Parameters

• $post_id
  (int) The attachment ID

• $quality
  (int) The requested image quality

• $width
  (int) The requested image width

• $height
  (int) The requested image height

• $crop
  (array) The requested image crop positions in percentages:

• $ratio
  (float) The requested image ratio

• $resize_path
  (string) The requested image file path

responsive_pics_file_saved_local

This action fires when ResponsivePics has successfully saved a resized image file locally.

Parameters

• $post_id
  (int) The attachment ID

• $file
  (array) The saved file containing:

responsive_pics_file_s3_uploaded

This action fires when WP Offload Media has uploaded the resized image file to your S3 storage.

Parameters

• $post_id
  (int) The attachment ID

• $file
  (array) The S3 uploaded file containing:

responsive_pics_file_deleted_local

This action fires when ResponsivePics has successfully deleted a resized image file locally.

Parameters

• $post_id
  (int) The attachment ID

• $file
  (string) The deleted image file path

responsive_pics_file_s3_deleted

This action fires when WP Offload Media has deleted a resized image file in your S3 storage.

Parameters

• $post_id
  (int) The attachment ID

• $file_paths
  (array) The deleted resized file paths in your S3 storage.

Features

S3 Offload

When you installed and activated the WP Offload Media (Lite) plugin, this library automatically:

• Will offload any resized/cropped image generated by this plugin to your configured S3 storage provider.
• Will delete any resized/cropped image generated by this plugin in your configured S3 storage provider when deleting an attachment.

NOTE

When the Remove Files From Server option is activated in the Offload Media Lite settings, this plugin will NOT remove any resized/cropped image generated by this plugin!

Lazyloading

When enabling the lazyload option in the get_picture or get_image functions or API endpoints with a boolean value true, this library automatically:

• adds a lazyload class to the <img> element.
• swaps the srcset with data-srcset attribute on the picture <source> or the <img> elements.

This will enable you to use a lazy loading plugin such as Lazysizes.

You can also set your own lazyload class by passing it to ResponsivePics library in your theme’s functions.php:

To install Lazysizes in your wordpress theme as a node module, run the following command from your theme directory:

npm

npm install --save lazysizes

Yarn

yarn add lazysizes

And import the package in your theme’s global javascript file:

When enabling lazyload with a string value native, this library automatically:

• adds the native loading="lazy" attribute to the <img> element.

LQIP (Low Quality Image Placeholder)

When enabling the lqip option in the get_image function or /responsive-pics/v1/image API endpoint, this library automatically:

• adds a blur-up class to the <img> element.
• adds a fallback src attribute on the <img> element with a low quality placeholder image with a default width of 100px.

This will enable you to style your placeholder image before the actual high quality image is loaded.

You can also set your own lqip class by passing it to ResponsivePics library in your theme’s functions.php:

Intrinsic Aspectratio

When enabling the intrinsic option in the get_picture function or /responsive-pics/v1/picture API endpoint, this library automatically:

• adds a intrinsic class to the <picture> element and a intrinsic__item class to the picture <img> element.
• adds data-aspectratio attributes on the picture <source> and <img> elements with the calculated source image ratio.

This will enable you to pre-occupy the space needed for an image by calculating the height from the image width or the width from the height with an intrinsic plugin such as the lazysizes aspectratio extension.

To use the Lazysizes aspectratio extension in your wordpress theme, first install lazysizes as a node module as described in the Lazyloading section and import the extension in your theme’s global javascript file:

Issues

Please submit any issues you experience with the ResponsivePics library over at Github.

Todo's

• Add Application Password Authentication to REST API endpoints.
• Add Gutenberg Blocks support.
• Add WPML (Media) support for focal point.
• Add multiple background images syntax support.
• Add bulk image delete functionality.

Maintainers

ResponsivePics is developed and maintained by:

@monokai (creator)
@twansparant (creator)

Copyright

Code and documentation copyright 2017-2023 by Clarify.
Code released under the MIT License.
Docs released under Creative Commons.