Middleman Simple Thumbnailer

Middleman Simple Thumbnailer is a Middleman extension that allows you to create image thumbnails by providing resize_to option to image_tag helper.

Installation

Put this line into your Gemfile:

gem 'middleman-simple-thumbnailer'

Usage

All mode

Enable the extension in config.rb:

activate :middleman_simple_thumbnailer

And modify your image_tag's by adding resize_to parameter:

= image_tag image, resize_to: '50x50', class: 'thumbnail'

You can also use the image_path helper the same way in place where you need only the path of the resized image:

<picture>
  <source srcset="<%= image_path 'original.jpg', resize_to: 1200 %>" media="(min-width: 900px)">
  <%= image_tag "original.jpg", resize_to: "400%", class: 'the-image-class' %>
</picture>

This extension use ImageMagick (via mini_magick) to resize the images. The resize_to format is therefore the one defined ny ImageMagick. The documentation can be found there.

Dynamic mode

This mode is the default operating mode for this extension. The images are generated according to their declaration in the helpers. See the known limitations paragraph below for known limitation in this mode.

Declarative mode

In this mode, the resized file are declared. They are then added to the sitemap and generated at the same time than the other files.

To activate this new mode, the option :use_specs must be used when activating the extension.

activate :middleman_simple_thumbnailer, use_specs: true

Then the resizing specifications must be declared in a special Middleman data file. By default the extension will look for data/simple_thumbnailer.yaml.

This file must contains a list of mappings with the following keys:

path: the relative path of the image file in the source\images folder. This can be a glob pattern (https://ruby-doc.org/core/Dir.html#method-c-glob) (still relative to the source\images folder).
resize_to: the ImageMagix resize parameter

example (in yaml, file data/simple_thumbnailer.yaml):

---
- path: original.jpg
  resize_to: 10x10
- path: "*.jpg"
  resize_to: 5x5

The use of the image_tag and image_path helpers stay the same.

In this mode if a resizing specification found in an image_tag or image_path helper is not declared in the specification data file, a warning is emitted and the data file is rewritten to include the resizing specification. If the specification file doesn't exist, it is created (this behavior can be configured).

options

Option	default value	Description
:use_cache_dev	`true`	In development, add a Rack middleware to serve the resized image from cache
:cache_dir	`'tmp/simple-thumbnailer-cache'`	Directory (relative to project root) for cached thumbnails.
:use_specs	`false`	Wether or not use resize specfication data file
:specs_data	`'simple_thumbnailer'`	name of the specification data file. It must follow the Middleman data file name convention.
:specs_data_default_format	`'yaml'`	defaut specification format (and extension). Can be 'yml', 'yaml', 'json'
:specs_data_save_old	`true`	save previous specification data file
:update_specs	`true`	Warn about missing image files in the specification file and add them to it. The spécification file will be overwritten.

Known limitation

In the dynamic mode, this extension is unable to update the sitemap. Some extensions (like middleman-s3_sync) uses the content of the sitemap to do their work. Therefore, the generated resized images will not be seen by such extensions, even if they are corectly generated.

Build/Development modes

During development:

if option use_cache_dev is set to true thumbnails will be created when accessed, and are served with a rack middleware from the cache folder.
Otherwise thumbnails will be created on fly and presented as a base64 strings.

During build thumbnails will be created as normal files and stored in same dir as their originals.

LICENSE

MIT