django-croppable-images

django-croppable-images is a reusable app that helps you easily add image cropping functionality to your Django projects.

When you use this app, your original images as well as their corresponding cropped versions will be saved to your default storage. The crop coordinates are also saved so that they can be displayed to and adjusted by your end-users via a seamless front-end interface implemented as a custom Django form field + widget (using Jcrop).

To use django-croppable-images, you will need to install django-imagekit which is used to manage the actual cropping of image files.

How to Use

Add a CroppableImageField to your model where you would otherwise have a stock Django ImageField.

Also add an ImageSpecField (from django-imagekit) to your model and set its image_field argument to the name of the CroppableImageField you created above. For the processors argument (the first positional argument in the ImageSpecField constructor), use the provided get_crop_processor() utility function and pass in the same image_field argument as before.

Here's an example:

from django.db import models
from imagekit.models import ImageSpecField
from croppable.fields import CroppableImageField
from croppable.utils import get_crop_processor

class MyFavoriteModel(models.Model):
    name = models.CharField(max_length=200)
    some_other_field = models.CharField(max_length=200)
    my_image = CroppableImageField(invalidate_on_save=['my_image_cropped'], upload_to='my_image_folder', blank=True)
    my_image_cropped = ImageSpecField(get_crop_processor(image_field='my_image'), image_field='my_image')

CroppableImageField is a model field that is just a subclass of Django's ImageField, so it takes all of the arguments supported by its superclass (e.g. upload_to and blank in the example above)

In most cases, you'll want to pass in the optional invalidate_on_save argument to your CroppableImageField and set it to a list containing just the name of your corresponding ImageSpecField (as is done in the above example). This tells django-image-kit that it needs to re-process the image modifications associated with each ImageSpecField in the list at some point after (or at the same time as) your model is saved. This is necessary so that the cropped image file is changed if the crop coordinates are changed.

If you're familiar with ImageKit, by "re-process" above, we are just calling invalidate() on the corresponding ImageSpecField. We recommend using ImageKit's non-default NonValidatingImageCacheBackend . In the context of django-croppable-images, all this does is make it so your cropped images are updated each time your model is saved. Simply add the following line to your settings:

IMAGEKIT_DEFAULT_IMAGE_CACHE_BACKEND = 'imagekit.imagecache.NonValidatingImageCacheBackend'

Finally, to hook up the front-end interface all you need to do is use the included CroppableImageField form field (as opposed to the model field above) to your ModelForm.

In the context of the Django Admin, you would just create your own ModelForm and have it use a CroppableImageField for the field that corresponds to your image. Then simply tell your ModelAdmin to use that form. Here's a full example:

from django import forms
from django.contrib import admin
from myapp.models import MyFavoriteModel
from croppable.forms import CroppableImageField

class MyFavoriteModelAdminForm(forms.ModelForm):
    my_image = CroppableImageField()

    class Meta:
        model = MyFavoriteModel

class MyFavoriteModelAdmin(admin.ModelAdmin):
    form = MyFavoriteModelAdminForm

admin.site.register(MyFavoriteModel, MyFavoriteModelAdmin)

Now on the Admin site for MyFavoriteModel you'll have an awesome Jcrop-powered widget that lets you define a crop region for your image. When you press save, your original image will be uploaded and a new image file will be saved that contains the cropped version.

To display the cropped image in a template, just use the attribute on your model that contains the ImageSpecField:

<img src="{% my_favorite_model_instance.my_image_cropped.url %}">

How it Works

The CroppableImageField model field subclasses the Django ImageField and uses its own CroppableImageFieldFile (a subclass of ImageFieldFile which overrides the file-saving functionality). Instead of saving just the filename to the database, CroppableImageFieldFile saves both the filename as well as the crop coordinates (in CSV format), separated by a configurable delimiter. To change the default, just set CROPPABLE_IMAGE_FIELD_DELIMITER to whatever you want it to be in your settings (note that this must contain only valid characters for use in UNIX filenames).

The CroppableImageField form field subclasses the Django MultiValueField form field and uses both an ImageField and CharField (for the crop coordinates). This form field appends the crop coordinates to the image's filename (along with the delimiter) and passes it off to the model field / field file which knows how to parse it.

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