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moved models in front of source groups in the advanced docs
This commit is contained in:
Saul Shanabrook
parent
deed81b963
commit
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1 changed files with 106 additions and 107 deletions
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@ -2,6 +2,112 @@ Advanced Usage
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**************
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Models
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======
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The ``ImageSpecField`` Shorthand Syntax
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---------------------------------------
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If you've read the README, you already know what an ``ImageSpecField`` is and
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the basics of defining one:
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.. code-block:: python
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from django.db import models
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from imagekit.models import ImageSpecField
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from imagekit.processors import ResizeToFill
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class Profile(models.Model):
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avatar = models.ImageField(upload_to='avatars')
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avatar_thumbnail = ImageSpecField(source='avatar',
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processors=[ResizeToFill(100, 50)],
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format='JPEG',
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options={'quality': 60})
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This will create an ``avatar_thumbnail`` field which is a resized version of the
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image stored in the ``avatar`` image field. But this is actually just shorthand
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for creating an ``ImageSpec``, registering it, and associating it with an
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``ImageSpecField``:
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.. code-block:: python
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from django.db import models
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from imagekit import ImageSpec, register
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from imagekit.models import ImageSpecField
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from imagekit.processors import ResizeToFill
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class AvatarThumbnail(ImageSpec):
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processors = [ResizeToFill(100, 50)]
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format = 'JPEG'
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options = {'quality': 60}
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register.generator('myapp:profile:avatar_thumbnail', AvatarThumbnail)
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class Profile(models.Model):
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avatar = models.ImageField(upload_to='avatars')
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avatar_thumbnail = ImageSpecField(source='avatar',
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spec_id='myapp:profile:avatar_thumbnail')
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Obviously, the shorthand version is a lot, well…shorter. So why would you ever
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want to go through the trouble of using the long form? The answer is that the
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long form—creating an image spec class and registering it—gives you a lot more
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power over the generated image.
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.. _dynamic-specs:
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Specs That Change
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-----------------
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As you'll remember from the README, an image spec is just a type of image
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generator that generates a new image from a source image. How does the image
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spec get access to the source image? Simple! It's passed to the constructor as
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a keyword argument and stored as an attribute of the spec. Normally, we don't
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have to concern ourselves with this; the ``ImageSpec`` knows what to do with the
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source image and we're happy to let it do its thing. However, having access to
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the source image in our spec class can be very useful…
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Often, when using an ``ImageSpecField``, you may want the spec to vary based on
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properties of a model. (For example, you might want to store image dimensions on
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the model and then use them to generate your thumbnail.) Now that we know how to
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access the source image from our spec, it's a simple matter to extract its model
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and use it to create our processors list. In fact, ImageKit includes a utility
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for getting this information.
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.. code-block:: python
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:emphasize-lines: 11-14
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from django.db import models
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from imagekit import ImageSpec, register
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from imagekit.models import ImageSpecField
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from imagekit.processors import ResizeToFill
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from imagekit.utils import get_field_info
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class AvatarThumbnail(ImageSpec):
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format = 'JPEG'
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options = {'quality': 60}
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@property
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def processors(self):
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model, field_name = get_field_info(self.source)
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return [ResizeToFill(model.thumbnail_width, thumbnail.avatar_height)]
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register.generator('myapp:profile:avatar_thumbnail', AvatarThumbnail)
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class Profile(models.Model):
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avatar = models.ImageField(upload_to='avatars')
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avatar_thumbnail = ImageSpecField(source='avatar',
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spec_id='myapp:profile:avatar_thumbnail')
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thumbnail_width = models.PositiveIntegerField()
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thumbnail_height = models.PositiveIntegerField()
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Now each avatar thumbnail will be resized according to the dimensions stored on
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the model!
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Of course, processors aren't the only thing that can vary based on the model of
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the source image; spec behavior can change in any way you want.
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.. _source-groups:
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Source Groups
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@ -75,110 +181,3 @@ Note that, since this source group doesnt send the `source_created` or
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`source_changed` signals, the corresponding cache file strategy callbacks
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would not be called for them.
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Models
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======
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The ``ImageSpecField`` Shorthand Syntax
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---------------------------------------
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If you've read the README, you already know what an ``ImageSpecField`` is and
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the basics of defining one:
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.. code-block:: python
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from django.db import models
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from imagekit.models import ImageSpecField
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from imagekit.processors import ResizeToFill
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class Profile(models.Model):
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avatar = models.ImageField(upload_to='avatars')
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avatar_thumbnail = ImageSpecField(source='avatar',
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processors=[ResizeToFill(100, 50)],
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format='JPEG',
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options={'quality': 60})
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This will create an ``avatar_thumbnail`` field which is a resized version of the
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image stored in the ``avatar`` image field. But this is actually just shorthand
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for creating an ``ImageSpec``, registering it, and associating it with an
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``ImageSpecField``:
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.. code-block:: python
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from django.db import models
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from imagekit import ImageSpec, register
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from imagekit.models import ImageSpecField
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from imagekit.processors import ResizeToFill
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class AvatarThumbnail(ImageSpec):
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processors = [ResizeToFill(100, 50)]
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format = 'JPEG'
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options = {'quality': 60}
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register.generator('myapp:profile:avatar_thumbnail', AvatarThumbnail)
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class Profile(models.Model):
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avatar = models.ImageField(upload_to='avatars')
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avatar_thumbnail = ImageSpecField(source='avatar',
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spec_id='myapp:profile:avatar_thumbnail')
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Obviously, the shorthand version is a lot, well…shorter. So why would you ever
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want to go through the trouble of using the long form? The answer is that the
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long form—creating an image spec class and registering it—gives you a lot more
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power over the generated image.
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.. _dynamic-specs:
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Specs That Change
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-----------------
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As you'll remember from the README, an image spec is just a type of image
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generator that generates a new image from a source image. How does the image
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spec get access to the source image? Simple! It's passed to the constructor as
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a keyword argument and stored as an attribute of the spec. Normally, we don't
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have to concern ourselves with this; the ``ImageSpec`` knows what to do with the
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source image and we're happy to let it do its thing. However, having access to
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the source image in our spec class can be very useful…
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Often, when using an ``ImageSpecField``, you may want the spec to vary based on
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properties of a model. (For example, you might want to store image dimensions on
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the model and then use them to generate your thumbnail.) Now that we know how to
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access the source image from our spec, it's a simple matter to extract its model
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and use it to create our processors list. In fact, ImageKit includes a utility
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for getting this information.
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.. code-block:: python
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:emphasize-lines: 11-14
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from django.db import models
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from imagekit import ImageSpec, register
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from imagekit.models import ImageSpecField
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from imagekit.processors import ResizeToFill
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from imagekit.utils import get_field_info
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class AvatarThumbnail(ImageSpec):
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format = 'JPEG'
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options = {'quality': 60}
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@property
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def processors(self):
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model, field_name = get_field_info(self.source)
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return [ResizeToFill(model.thumbnail_width, thumbnail.avatar_height)]
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register.generator('myapp:profile:avatar_thumbnail', AvatarThumbnail)
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class Profile(models.Model):
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avatar = models.ImageField(upload_to='avatars')
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avatar_thumbnail = ImageSpecField(source='avatar',
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spec_id='myapp:profile:avatar_thumbnail')
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thumbnail_width = models.PositiveIntegerField()
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thumbnail_height = models.PositiveIntegerField()
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Now each avatar thumbnail will be resized according to the dimensions stored on
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the model!
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Of course, processors aren't the only thing that can vary based on the model of
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the source image; spec behavior can change in any way you want.
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