How to Use Assetic For Image Optimization with Twig Functions

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How to Use Assetic For Image Optimization with Twig Functions

Amongst its many filters, Assetic has four filters which can be used for on-the-fly image optimization. This allows you to get the benefits of smaller file sizes without having to use an image editor to process each image. The results are cached and can be dumped for production so there is no performance hit for your end users.

Using Jpegoptim

Jpegoptim is a utility for optimizing JPEG files. To use it with Assetic, add the following to the Assetic config:

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# app/config/config.yml
assetic:
    filters:
        jpegoptim:
            bin: path/to/jpegoptim

Note

Notice that to use jpegoptim, you must have it already installed on your system. The bin option points to the location of the compiled binary.

It can now be used from a template:

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{% image '@AcmeFooBundle/Resources/public/images/example.jpg'
    filter='jpegoptim' output='/images/example.jpg' %}
    <img src="{{ asset_url }}" alt="Example"/>
{% endimage %}

Removing all EXIF Data

By default, running this filter only removes some of the meta information stored in the file. Any EXIF data and comments are not removed, but you can remove these by using the strip_all option:

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# app/config/config.yml
assetic:
    filters:
        jpegoptim:
            bin: path/to/jpegoptim
            strip_all: true

Lowering Maximum Quality

The quality level of the JPEG is not affected by default. You can gain further file size reductions by setting the max quality setting lower than the current level of the images. This will of course be at the expense of image quality:

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# app/config/config.yml
assetic:
    filters:
        jpegoptim:
            bin: path/to/jpegoptim
            max: 70

Shorter syntax: Twig Function

If you're using Twig, it's possible to achieve all of this with a shorter syntax by enabling and using a special Twig function. Start by adding the following config:

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# app/config/config.yml
assetic:
    filters:
        jpegoptim:
            bin: path/to/jpegoptim
    twig:
        functions:
            jpegoptim: ~

The Twig template can now be changed to the following:

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<img src="{{ jpegoptim('@AcmeFooBundle/Resources/public/images/example.jpg') }}" alt="Example"/>

You can specify the output directory in the config in the following way:

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# app/config/config.yml
assetic:
    filters:
        jpegoptim:
            bin: path/to/jpegoptim
    twig:
        functions:
            jpegoptim: { output: images/*.jpg }
This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.