django-stdimage

Django Standardized Image Field

This package has been deprecated in favor of django-pictures.

Migration Instructions

First, make sure you understand the differences between the two packages and how to serve images in a modern web application via the picture-Element.

Next, follow the setup instructions for django-pictures.

Once you are set up, change your models to use the new PictureField and provide the aspect_ratios you’d like to serve. Do create migrations just yet.

This step should be followed by changing your templates and frontend. The new placeholders feature for local development should help you to do this almost effortlessly.

Finally, run makemigrations and replace the AlterField operation with AlterPictureField.

We highly recommend to use Django’s image_width and image_height fields, to avoid unnecessary IO. If you can add these fields to your model, you can use the following snippet to populate them:

import django.core.files.storage
from django.db import migrations, models
import pictures.models
from pictures.migrations import AlterPictureField

def forward(apps, schema_editor):
    for obj in apps.get_model("my-app.MyModel").objects.all().iterator():
        obj.image_width = obj.logo.width
        obj.image_height = obj.logo.height
        obj.save(update_fields=["image_height", "image_width"])

def backward(apps, schema_editor):
    apps.get_model("my-app.MyModel").objects.all().update(
        image_width=None,
        image_height=None,
    )

class Migration(migrations.Migration):
    dependencies = [
        ('my-app', '0001_initial'),
    ]

    operations = [
        migrations.AddField(
            model_name="mymodel",
            name="image_height",
            field=models.PositiveIntegerField(editable=False, null=True),
        ),
        migrations.AddField(
            model_name="mymodel",
            name="image_width",
            field=models.PositiveIntegerField(editable=False, null=True),
        ),
        migrations.RunPython(forward, backward),
        AlterPictureField(
            model_name="mymodel",
            name="image",
            field=pictures.models.PictureField(
                aspect_ratios=["3/2", "3/1"],
                breakpoints={"desktop": 1024, "mobile": 576},
                container_width=1200,
                file_types=["WEBP"],
                grid_columns=12,
                height_field="image_height",
                pixel_densities=[1, 2],
                storage=django.core.files.storage.FileSystemStorage(),
                upload_to="pictures/",
                verbose_name="image",
                width_field="image_width",
            ),
        ),
    ]

Why would I want this?

This is a drop-in replacement for the Django ImageField that provides a standardized way to handle image uploads. It is designed to be as easy to use as possible, and to provide a consistent interface for all image fields. It allows images to be presented in various size variants (eg:thumbnails, mid, and hi-res versions) and it provides a way to handle images that are too large with validators.

Features

Django Standardized Image Field implements the following features:

Django-Storages compatible (eg: S3, Azure, Google Cloud Storage, etc)
Resizes images to different sizes
Access thumbnails on model level, no template tags required
Preserves original images
Can be rendered asynchronously (ie as a Celery job)
Restricts acceptable image dimensions
Renames a file to a standardized name format (using a callable upload_to function, see below)

Installation

Simply install the latest stable package using the following command:

pip install django-stdimage
# or
pipenv install django-stdimage

and add 'stdimage' to INSTALLED_APPs in your settings.py, that’s it!

Usage

Now it’s instally you can use either: StdImageField or JPEGField.

StdImageField works just like Django’s own ImageField except that you can specify different size variations.

The JPEGField is identical to the StdImageField but all images are converted to JPEGs, no matter what type the original file is.

Variations

Variations are specified within a dictionary. The key will be the attribute referencing the resized image. A variation can be defined both as a tuple or a dictionary.

Example:

from django.db import models
from stdimage import StdImageField, JPEGField


class MyModel(models.Model):
    # works just like django's ImageField
    image = StdImageField(upload_to='path/to/img')

    # creates a thumbnail resized to maximum size to fit a 100x75 area
    image = StdImageField(upload_to='path/to/img',
                          variations={'thumbnail': {'width': 100, 'height': 75}})

    # is the same as dictionary-style call
    image = StdImageField(upload_to='path/to/img', variations={'thumbnail': (100, 75)})

    # JPEGField variations are converted to JPEGs.
    jpeg = JPEGField(
        upload_to='path/to/img',
        variations={'full': (None, None), 'thumbnail': (100, 75)},
    )

    # creates a thumbnail resized to 100x100 croping if necessary
    image = StdImageField(upload_to='path/to/img', variations={
        'thumbnail': {"width": 100, "height": 100, "crop": True}
    })

    ## Full ammo here. Please note all the definitions below are equal
    image = StdImageField(upload_to='path/to/img', blank=True, variations={
        'large': (600, 400),
        'thumbnail': (100, 100, True),
        'medium': (300, 200),
    }, delete_orphans=True)

To use these variations in templates use myimagefield.variation_name.

Example:

<a href=""><img alt="" src=""/></a>

Upload to function

You can use a function for the upload_to argument. Using [Django Dynamic Filenames][dynamic_filenames].[dynamic_filenames]: https://github.com/codingjoe/django-dynamic-filenames

This allows images to be given unique paths and filenames based on the model instance.

Example

from django.db import models
from stdimage import StdImageField
from dynamic_filenames import FilePattern

upload_to_pattern = FilePattern(
    filename_pattern='my_model/{app_label:.25}/{model_name:.30}/{uuid:base32}{ext}',
)


class MyModel(models.Model):
    # works just like django's ImageField
    image = StdImageField(upload_to=upload_to_pattern)

Validators

The StdImageField doesn’t implement any size validation out-of-the-box. However, Validation can be specified using the validator attribute and using a set of validators shipped with this package. Validators can be used for both Forms and Models.

Example

from django.db import models
from stdimage.validators import MinSizeValidator, MaxSizeValidator
from stdimage.models import StdImageField


class MyClass(models.Model):
    image1 = StdImageField(validators=[MinSizeValidator(800, 600)])
    image2 = StdImageField(validators=[MaxSizeValidator(1028, 768)])

CAUTION: The MaxSizeValidator should be used with caution. As storage isn’t expensive, you shouldn’t restrict upload dimensions. If you seek prevent users form overflowing your memory you should restrict the HTTP upload body size.

Deleting images

Django dropped support for automated deletions in version 1.3.

Since version 5, this package supports a delete_orphans argument. It will delete orphaned files, should a file be deleted or replaced via a Django form and the object with the StdImageField be deleted. It will not delete files if the field value is changed or reassigned programatically. In these rare cases, you will need to handle proper deletion yourself.

from django.db import models
from stdimage.models import StdImageField


class MyModel(models.Model):
    image = StdImageField(
        upload_to='path/to/files',
        variations={'thumbnail': (100, 75)},
        delete_orphans=True,
        blank=True,
    )

Async image processing

Tools like celery allow to execute time-consuming tasks outside of the request. If you don’t want to wait for your variations to be rendered in request, StdImage provides you the option to pass an async keyword and a ‘render_variations’ function that triggers the async task. Note that the callback is not transaction save, but the file variations will be present. The example below is based on celery.

tasks.py:

from django.apps import apps

from celery import shared_task

from stdimage.utils import render_variations


@shared_task
def process_photo_image(file_name, variations, storage):
    render_variations(file_name, variations, replace=True, storage=storage)
    obj = apps.get_model('myapp', 'Photo').objects.get(image=file_name)
    obj.processed = True
    obj.save()

models.py:

from django.db import models
from stdimage.models import StdImageField

from .tasks import process_photo_image

def image_processor(file_name, variations, storage):
    process_photo_image.delay(file_name, variations, storage)
    return False  # prevent default rendering

class AsyncImageModel(models.Model):
    image = StdImageField(
        # above task definition can only handle one model object per image filename
        upload_to='path/to/file/', # or use a function
        render_variations=image_processor  # pass boolean or callable
    )
    processed = models.BooleanField(default=False)  # flag that could be used for view querysets

Re-rendering variations

You might have added or changed variations to an existing field. That means you will need to render new variations. This can be accomplished using a management command.

python manage.py rendervariations 'app_name.model_name.field_name' [--replace] [-i/--ignore-missing]

The replace option will replace all existing files. The ignore-missing option will suspend ‘missing source file’ errors and keep rendering variations for other files. Otherwise, the command will stop on first missing file.

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