django-imagekit-cropper 1.15

Allow users to manually specify image variant crops

# django-imagekit-cropper
A library to enhance django-imagekit which allows you to specify your image variant crops:


**InstanceSpecField** This is a class that extends ImageSpecField which passes the model instance to
the processors so that you can access other model fields to process the image.

**InstanceFormatSpecField** This is a class that extends InstanceSpecField and can dynamically choose the image format (e.g. JPEG, PNG, GIF). PNGs have a much larger file size than JPEGs, but sometimes it's worth the filesize; this allows the admins to control on a per-image basis. Just pass a reference to the model field that returns a PIL-compatible file format.

**ImageCropField** This is a custom model field for setting the image crop. This uses a custom
widget to allow admins to visually crop the image.

**PositionCrop** This a custom processor which recieves the model instance and crops the image
using the image source and the value of the image crop field.

**FormatProcessor** This is a custom processor which implements resizing and outputs to a dynamic format.

**PositionAndFormatCrop** This processor extends PositionCrop and also implements dynamic format.

**WARNING:** This library is in very early alpha stages. I have only tested this on version django-imagekit==3.2.5

## Example Usage
```
$ pip install django-imagekit-cropper
```

```
#settings.py

INSTALLED_APPS = (
...
imagekit_cropper,
...
)
```


```python
#models.py

from imagekit_cropper.fields import ImageCropField, InstanceSpecField, InstanceFormatSpecField
from imagekit_cropper.processors import PositionCrop, PositionAndFormatCrop, FormatProcessor

image = models.ImageField(blank=True, null=True)

#Example 1 - BASIC CROP FIELD
width_1200_wide_crop_properties = {
'source':'image',
'crop_field':'width_1200_wide_crop',
'resize_method':'fill',
'width':1200,
'height':750,
'upscale':True
}
width_1200_wide_crop = ImageCropField(null=True, blank=True,
properties=width_1200_wide_crop_properties)

width_1200_wide = InstanceSpecField(
source=width_1200_wide_crop_properties['source'],
options={'quality': 85},
processors=[PositionCrop(width_1200_wide_crop_properties)])

#Example 2 - DYNAMIC FORMAT FIELD


width_1200_crop_properties = {
'source':'image',
'format_field':'get_format',
'resize_method':'fit',
'width':1200,
'height':None,
'upscale':False
}
width_1200 = InstanceFormatSpecField(
source=width_1200_crop_properties['source'],
format_field=width_1200_crop_properties['format_field'],
options={'quality': 95},
processors=[FormatProcessor(width_1200_crop_properties)])

use_png = models.BooleanField( default = False,
verbose_name='Use .PNG (instead of .JPG)')

@property
def get_format(self):
if self.use_png:
return 'PNG'
return 'JPEG'


#Example 3 - TWO SPECS USING THE SAME CROP

square_crop_properties = {
'source':'image',
'crop_field':'square_crop',
'format_field':'get_format',
'resize_method':'fill',
'aspect_ratio':1,
'min_width':400,
'min_height':400,
'upscale':False
}
square_crop = ImageCropField(null=True, blank=True, properties=square_crop_properties)

square_200_crop_properties = copy.copy(square_crop_properties)
square_200_crop_properties['width'] = 200
square_200_crop_properties['height'] = 200

square_200 = InstanceSpecField(
format='PNG',
source=square_200_crop_properties['source'],
options={'quality': 85},
processors=[PositionCrop(square_200_crop_properties)]
)

square_400_crop_properties = copy.copy(square_crop_properties)
square_400_crop_properties['width'] = 400
square_400_crop_properties['height'] = 400

square_400 = InstanceFormatSpecField(
source=square_400_crop_properties['source'],
format_field=square_400_crop_properties['format_field'],
options={'quality': 85},
processors=[PositionAndFormatCrop(square_400_crop_properties)]
)

```

```python
#admin.py

from .forms import ImageAdminForm

class ImageAdmin(models.ModelAdmin):
form = ImageAdminForm

```

```python
#forms.py

from django import forms
from imagekit_cropper.widgets import ImageCropWidget
from .models import Image


class ImageAdminForm(forms.ModelForm):
square_150_crop = forms.CharField(widget=ImageCropWidget(properties=Image.square_150_crop_properties, help_text=Image.help['square_150_crop']))

class Meta:
model = Image

```

To generate images, you'll need to use this modified version of the generateimages command:
```
$ python manage.py generateimages_cropped
```