How to Use Assetic for Image Optimization with Twig Functions
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Read the updated version of this page for Symfony 7.1 (the current stable version).
Caution
Starting from Symfony 2.8, Assetic is no longer included by default in the Symfony Standard Edition. Refer to this article to learn how to install and enable Assetic in your Symfony application.
Among 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, make
sure to have it already installed on your system and then, configure its location
using the bin
option of the jpegoptim
filter:
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# app/config/config.yml
assetic:
filters:
jpegoptim:
bin: path/to/jpegoptim
It can now be used from a template:
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{% image '@AppBundle/Resources/public/images/example.jpg'
filter='jpegoptim' output='/images/example.jpg' %}
<img src="{{ asset_url }}" alt="Example"/>
{% endimage %}
Removing all EXIF Data
By default, the jpegoptim
filter removes some meta information stored
in the image. To remove all EXIF data and comments, set the strip_all
option
to true
:
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# app/config/config.yml
assetic:
filters:
jpegoptim:
bin: path/to/jpegoptim
strip_all: true
Lowering Maximum Quality
By default, the jpegoptim
filter doesn't alter the quality level of the JPEG
image. Use the max
option to configure the maximum quality setting (in a
scale of 0
to 100
). The reduction in the image file size will of course
be at the expense of its 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 configuration:
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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('@AppBundle/Resources/public/images/example.jpg') }}" alt="Example"/>
You can also specify the output directory for images in the Assetic configuration file:
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# app/config/config.yml
assetic:
filters:
jpegoptim:
bin: path/to/jpegoptim
twig:
functions:
jpegoptim: { output: images/*.jpg }
Tip
For uploaded images, you can compress and manipulate them using the LiipImagineBundle community bundle.