Generate <img> markup block for an image.
Project description
A module to generate performant HTML image markup for images. The markup will:
Use data-src attributes for lazysizes
Use predefined srcset break points
Resize assets.ubuntu.com images with ?w=XX&h=XX query parameters
Prefix all image URLs with cloudinary proxy URLs, for CDN and image transformations
Parameters
url (mandatory string): The url to an image (e.g. https://assets.ubuntu.com/v1/9f6916dd-k8s-prometheus-light.png)
alt (mandatory string): Alt text to describe the image
width (mandatory integer): The number of pixels wide the image should be
height (mandatory integer): The number of pixels high the image should be
hi_def (mandatory boolean): Has an image been uploaded 2x the width and height of the desired size
extra_classes (optional): Class string to add to img element
extra attributes (optional): Extra <img> attributes (e.g. id) can be passed as additional arguments
Usage
The image_template function can be used directly to generate image Markup.
from canonicalwebteam import image_template
image_markup = image_template(
url="https://assets.ubuntu.com/v1/9f6916dd-k8s-prometheus-light.png",
alt="Operational dashboard",
width="1040",
height="585",
hi_def=True
)However, the most common usage is to add it to Django or Flask template contexts, as an image function.
Add lazysizes
The markup generated will use lazysizes format - it will use data-src instead of src and add the lazyload class.
Therefore to use this plugin you need to have lazysizes loaded on your pages. The simplest way to achieve this is to include this in your <head>:
<script src="https://assets.ubuntu.com/v1/842d27d3-lazysizes.min.js" async=""></script>Django usage
Add it as a template tag:
# myapp/templatetags.py
from canonicalwebteam import image_template
from django import template
from django.utils.safestring import mark_safe
register = template.Library()
@register.simple_tag
def image(*args, **kwargs):
return mark_safe(image_template(*args, **kwargs))
# settings.py
TEMPLATES[0]["OPTIONS"]["builtins"].append("myapp.templatetags")Use it in templates:
# templates/mytemplate.html
{% image url="https://assets.ubuntu.com/v1/9f6916dd-k8s-prometheus-light.png" alt="Operational dashboard" width="1040" height="585" hi_def=True %}Flask usage
Add it as a template tag:
# app.py
from canonicalwebteam import image_template
from flask import Flask
app = Flask(__name__)
@app.context_processor
def utility_processor():
return {"image": image_template}Use it in templates:
# templates/mytemplate.html
{{
image(
url="https://assets.ubuntu.com/v1/9f6916dd-k8s-prometheus-light.png",
alt="Operational dashboard",
width="1040",
height="585",
hi_def: True,
) | safe
}}Generated markup
All the above examples will generate the following markup:
<img
data-srcset="https://res.cloudinary.com/canonical/image/fetch/q_auto,f_auto,fl_sanitize,w_2080,h_1170/https%3A//assets.ubuntu.com/v1/9f6916dd-k8s-prometheus-light.png x2"
data-src="https://res.cloudinary.com/canonical/image/fetch/q_auto,f_auto,fl_sanitize,w_1040,h_585/https%3A//assets.ubuntu.com/v1/9f6916dd-k8s-prometheus-light.png"
alt="Operational dashboard"
width="1040"
height="585"
class="lazyload"
/>
<noscript>
<img
srcset="https://res.cloudinary.com/canonical/image/fetch/q_auto,f_auto,fl_sanitize,w_2080,h_1170/https%3A//assets.ubuntu.com/v1/9f6916dd-k8s-prometheus-light.png x2"
src="https://res.cloudinary.com/canonical/image/fetch/q_auto,f_auto,fl_sanitize,w_1040,h_585/https%3A//assets.ubuntu.com/v1/9f6916dd-k8s-prometheus-light.png"
alt="Operational dashboard"
width="1040"
height="585"
/>
</noscript>File sizes
Source: https://assets.ubuntu.com/v1/9f6916dd-k8s-prometheus-light.png 2560 x 1440 - 300.62kb
Asset server x2 resize: https://assets.ubuntu.com/v1/9f6916dd-k8s-prometheus-light.png?w=2080&h=1170 2080 x 1170 - 595.67kb
Asset server resize: https://assets.ubuntu.com/v1/9f6916dd-k8s-prometheus-light.png?w=1040&h=585 1040 x 585 - 221.21kb
Asset server resize x2 + Cloudinary x2 resize: https://res.cloudinary.com/canonical/image/fetch/q_auto,f_auto,fl_sanitize/https%3A//assets.ubuntu.com/v1/9f6916dd-k8s-prometheus-light.png%3Fw%3D2080%26h%3D1170 2080 x 1170 - 194.97kb
Asset server resize x1 + Cloudinary x1 resize: https://res.cloudinary.com/canonical/image/fetch/q_auto,f_auto,fl_sanitize/https%3A//assets.ubuntu.com/v1/9f6916dd-k8s-prometheus-light.png%3Fw%3D1040%26h%3D585 1040 x 585 - 109.38kb
Cloudinary x2 resize: https://res.cloudinary.com/canonical/image/fetch/q_auto,f_auto,fl_sanitize,w_2080,h_1170/https://assets.ubuntu.com/v1/9f6916dd-k8s-prometheus-light.png 2080 x 1170 - 163.38
Cloudinary x1 resize: https://res.cloudinary.com/canonical/image/fetch/q_auto,f_auto,fl_sanitize,w_1040,h_585/https://assets.ubuntu.com/v1/9f6916dd-k8s-prometheus-light.png 1040 x 585 - 62.80kb
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