python - django imagekit 处理器 : use dimensions stored in database

Question

我有一个模型，其中缩略图宽度在父对象 (ForeignKey) 之间变化。我需要能够将此信息提供给 Imagekit 处理器。这是我的:

class Wall(models.Model):
    #...
    width = models.SmallIntegerField(null=True, blank=True)
    #...


class Poster(models.Model):
    wall = models.ForeignKey(Wall, related_name='posters')
    #...
    original_image = models.ImageField(upload_to=upload_image_to)

    def __init__(self, *args, **kwargs):
        self.thumbnail = ImageSpecField([
                Adjust(contrast=1.2, sharpness=1.1),
                SmartResize(height=163, width=self.wall.width)
            ],
            image_field='original_image', format='PNG'
        )

        super(Poster, self).__init__(*args, **kwargs)
    #...

但如果我这样做，什么也不会发生，甚至连缩略图 url 都不会生成。

以下将导致此异常:
AttributeError: 'ForeignKey' 对象没有属性 'width'

class Poster(models.Model):
    wall = models.ForeignKey(Wall, related_name='posters')
    #...
    original_image = models.ImageField(upload_to=upload_image_to)

    thumbnail = ImageSpecField([
            Adjust(contrast=1.2, sharpness=1.1),
            SmartResize(height=163, width=wall.width)
        ],
        image_field='original_image', format='PNG'
    )
    #...

Answer 1

#1 答案不适合当前版本的 django-imagekit (3.0.3)。我找到了官方解决方案。请引用 http://django-imagekit.readthedocs.org/en/latest/advanced_usage.html#specs-that-change