# django-admin-thumbnails
A Django app to assist in adding thumbnails for your model's image fields to admin list views and forms in a reasonably DRY manner.
## Rationale
When working with models that include `ImageField`s, `FileField`s or when using `ThumbnailerImageField` from `easy_thumbnails`, it can often be desirable to include a thumbnail preview of the field as part of the admin form, fieldset or in list views. Various methods to achieve this exist but all seem to involve a degree of duplication. I've made a few attempts to DRY out such code over the years and this library represents my most recent solution. So, please enjoy!
## Compatibility
I've not exhaustively tested all the below combinations, however I believe this table to be accurate.
| | Django 1.10 | 1.11 | 2.0 | 2.1 | 2.2 | 3.0 | 3.1 | 3.2 | 4.0 | 4.1 | 4.2 |
| -------------: | :---------: | :--: | :-: | :-: | :-: | :-: | :-: | :-: | :-: | :-: | :-: |
| **Python** 2.7 | ✔ | ✔ | | | | | | | | | |
| 3.6 | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | | | |
| >= 3.8 | | | | | | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ |
## Installation
```
$ pip install django-admin-thumbnails
```
## Usage
The app adds fields to your `ModelAdmin` or `*Inline` class; one for each thumbnail you want to display. These are appended to the class's `readonly_fields` tuple (unless you specify otherwise) so they will be displayed at the bottom of your admin form, or you can include them by name in your `fieldsets` or `list_display` definitions.
`django-admin-thumbnails` will handle `ImageField`, `FileField` (so you can use SVG, for example) and (if `easy_thumbnails` is installed) `ThumbnailerImageField`. In the latter case a thumbnail alias will be used, which you can specify in settings.
### Basic usage
To create an admin thumbnail field, decorate your `ModelAdmin` or `*Inline` class and optionally specify what to do with the newly created field.
Assuming a model like the following:
```python
class Person(models.Model):
name = models.CharField('Name', max_length=100)
image = models.ImageField('Image')
# ...
```
In the simplest use-case, to add a thumbnail field to the bottom of the admin form, simply decorate the `ModelAdmin` or `*Inline` class (the order of decorators is important), supplying the name of the field from which the thumbnail will be taken:
```python
import admin_thumbnails
@admin.register(models.Person)
@admin_thumbnails.thumbnail('image')
class PersonAdmin(admin.ModelAdmin):
pass
```
This will add a field called `image_thumbnail` (`FOO_thumbnail` where `FOO` is the origin field's name) to your `ModelAdmin` or `*Inline` definition. To override the title given to the new field, pass a second string argument to the decorator:
```python
@admin_thumbnails.thumbnail('image', 'Thumbnail')
```
To add the thumbnail to the columns shown in the model's list view, add the new field name to `list_display`:
```python
@admin.register(models.Person)
@admin_thumbnails.thumbnail('image')
class PersonAdmin(admin.ModelAdmin):
list_display = ('name', 'image_thumbnail')
```
Or include it in your `fieldsets` similarly:
```python
@admin.register(models.Person)
@admin_thumbnails.thumbnail('image')
class PersonAdmin(admin.ModelAdmin):
fieldsets = (
(None, {
'fields': ('name', 'image_thumbnail'),
}),
)
```
### Using thumbnails in the list view only
By default the new field will be appended to the `readonly_fields` tuple – if this is undesirable (e.g. if you want to include the thumbnail in the list view but _not_ in the default form fields), pass `append=False` to the decorator:
```python
@admin.register(models.Person)
@admin_thumbnails.thumbnail('image', append=False)
class PersonAdmin(admin.ModelAdmin):
list_display = ('name', 'image_thumbnail')
```
This isn't necessary if you're using `fieldsets`, as by doing so you will control the inclusion (or omission) and position of the thumbnail field.
### Using a property on the model as the thumbnail source
As of version 0.2.7, the name passed to the `thumbnail` decorator can refer to a property on the model rather than a field. For example:
```python
class Person(models.Model):
# ...
@property
def primary_image(self):
if self.images.count():
return self.images.first().image
return None
```
Provided the specified property returns an instance of a `FieldFile` (i.e. a file stored in a field that is an instance of Django's `ImageField`, `FileField`, or `easy_thumbnails`' `ThumbnailerImageField`), this will work as normal.
This also works with Django's [`cached_property`](https://docs.djangoproject.com/en/dev/ref/utils/#django.utils.functional.cached_property) decorator.
### Adding a background to displayed thumbnails
If your field contains images that are designed to be shown on a dark background, you can supply `background=True` to the decorator to add one to the thumbnail (via CSS) when displayed:
```python
@admin_thumbnails.thumbnail('image', background=True)
```
If you're using `easy_thumbnails` and want to override the alias used to generate your thumbnail on a per-field basis (as opposed to using the `ADMIN_THUMBNAIL_THUMBNAIL_ALIAS` setting; see below), you can use the `alias` argument to the decorator:
```python
@admin_thumbnails.thumbnail('image', alias='admin_thumbnail_alternative')
```
## Configuration
### `ADMIN_THUMBNAIL_DEFAULT_LABEL`
**Default:** `'Preview'`
Setting this overrides the default column name / title used by thumbnails.
### `ADMIN_THUMBNAIL_FIELD_SUFFIX`
**Default:** `'_thumbnail'`
Setting this overrides the suffix given to newly created thumbnail fields. Change if you have collision issues with other field names you want to use. Don't forget to update `list_display` and/or `fieldsets` in your `ModelAdmin` as necessary.
### `ADMIN_THUMBNAIL_THUMBNAIL_ALIAS`
**Default:** `'admin_thumbnail'`
If `easy_thumbnails` is installed and available, any model field using `ThumbnailerImageField` will be resized using a thumbnail alias called `admin_thumbnail` if it's defined. You can either define this alias in your settings (more info from the `easy_thumbnails` documentation [here](https://easy-thumbnails.readthedocs.io/en/stable/usage/#thumbnail-aliases)) or supply a different alias name as the value of this setting.
### `ADMIN_THUMBNAIL_STYLE`
**Default:** `{'display': 'block', 'width': '100px', 'height': 'auto'}`
A dictionary of CSS property/value pairs that will be added to the `style` attribute of any thumbnail image when output in the admin. Override to supply your own styles.
### `ADMIN_THUMBNAIL_BACKGROUND_STYLE`
**Default:** `{'background': '#000'}`
A dictionary of CSS property/value pairs added when the `background=True` option is used (see **Usage** above). Override to supply your own styles. Note that these styles are used _in addition_ to any defined in `ADMIN_THUMBNAIL_STYLE`.
## Development installation
If working locally on the package you can install the development tools via `pip`:
```shell
$ pip install -e .[dev]
```
To lint with `flake8`:
```shell
$ flake8
```
## Issues, suggestions, contributions
...are welcome on GitHub. Thanks for your interest in `django-admin-thumbnails`!