Python Django ImageKit：添加水印并创建缩略图

我需要适合用户上传的图像到1000px，并把水印。我还需要创建缩略图（没有水印）

问题是缩略图是从已经处理过的图像创建的。

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如果不应保存原始图像，如何从原始图像创建缩略图？

我使用easy_缩略图和信号解决了此问题：

# settings.py
THUMBNAIL_ALIASES = {
    'gallery': {
        'small': {'size': (200, 200), 'crop': True},
    },
}
THUMBNAIL_PROCESSORS = easy_thumbnails_defaults.THUMBNAIL_PROCESSORS + (
    'gallery.models.watermark_processor',
)

# gallery/models.py
def watermark_processor(image, watermark=False, **kwargs):
    if watermark:
        draw = ImageDraw.Draw(image)
        draw.line((0, 0) + image.size, fill=128)
        draw.line((0, image.size[1], image.size[0], 0), fill=128)
    return image

class Photo(models.Model):
    image = ThumbnailerImageField(upload_to='photo',
                                  resize_source={
                                      'size': (1000, 1000),
                                      'watermark': True,
                                  })

@receiver(pre_save, sender=Photo)
def make_thumbnail(sender, instance, **kwargs):
    easy_thumbnails.files.generate_all_aliases(instance.image, False)

不幸的是，将此信号技巧用于ImageKit（如

instance.thumboil.generate（）

）会引发I/O错误

# settings.py
THUMBNAIL_ALIASES = {
    'gallery': {
        'small': {'size': (200, 200), 'crop': True},
    },
}
THUMBNAIL_PROCESSORS = easy_thumbnails_defaults.THUMBNAIL_PROCESSORS + (
    'gallery.models.watermark_processor',
)

# gallery/models.py
def watermark_processor(image, watermark=False, **kwargs):
    if watermark:
        draw = ImageDraw.Draw(image)
        draw.line((0, 0) + image.size, fill=128)
        draw.line((0, image.size[1], image.size[0], 0), fill=128)
    return image

class Photo(models.Model):
    image = ThumbnailerImageField(upload_to='photo',
                                  resize_source={
                                      'size': (1000, 1000),
                                      'watermark': True,
                                  })

@receiver(pre_save, sender=Photo)
def make_thumbnail(sender, instance, **kwargs):
    easy_thumbnails.files.generate_all_aliases(instance.image, False)