Question

拥有缩略图像的Django模型，如：

class Thumb(models.Model):
    thumb = models.ImageField(upload_to='uploads/thumb/', null=True, default=None)

该视图使用pillow包生成缩略图，并应使用以下代码将其保存在Thumb实例中：

image.thumbnail((50, 50))
inst.thumb.save('thumb.jpg', ???)

在image为inst.thumb.save制作???数据的正确方法是什么？

我能够让下面的工作：

thumb_temp = NamedTemporaryFile()
image.save(thumb_temp, 'JPEG', quality=80)
thumb_temp.flush()
inst.thumb.save('thumb.jpg', File(thumb_temp))
thumb_temp.close()  # Probably required to ensure temp file delete at close

但是编写一个临时文件只是为了将内部数据传递给inst.thumb.save似乎相当笨拙，所以我想知道是否有更优雅的方法来做到这一点。 Django class NamedTemporaryFile的文档。

Answer 1

这是一个工作示例（Python3，django 1.11），它从Model.ImageField获取图像，使用PIL（Pillow）对其执行调整大小操作，然后将生成的文件保存到同一个ImageField。希望这应该很容易适应您必须对模型图像进行的任何处理。

from io import BytesIO
from django.core.files.uploadedfile import InMemoryUploadedFile
from django.core.files.base import ContentFile

IMAGE_WIDTH = 100
IMAGE_HEIGHT = 100

def resize_image(image_field, width=IMAGE_WIDTH, height=IMAGE_HEIGHT, name=None):
    """
    Resizes an image from a Model.ImageField and returns a new image as a ContentFile
    """
    img = Image.open(image_field)
    if img.size[0] > width or img.size[1] > height:
        new_img = img.resize((width, height))
    buffer = BytesIO()
    new_img.save(fp=buffer, format='JPEG')
    return ContentFile(buffer.getvalue())

#assuming your Model instance is called `instance`
image_field = instance.image_field
img_name = 'my_image.jpg'
img_path = settings.MEDIA_ROOT + img_name

pillow_image = resize_image(
                  image_field,
                  width=IMAGE_WIDTH,
                  height=IMAGE_HEIGHT,
                  name=img_path)

image_field.save(img_name, InMemoryUploadedFile(
     pillow_image,       # file
     None,               # field_name
     img_name,           # file name
     'image/jpeg',       # content_type
     pillow_image.tell,  # size
     None)               # content_type_extra
)

Answer 2

您可以为模型创建pre_save接收器：

from io import BytesIO
from functools import partial
from django.db import models
from django.core.files.uploadedfile import InMemoryUploadedFile
from PIL import Image

class Article(models.Model):
    title = models.CharField(max_length=120)
    slug = models.SlugField(max_length=120, unique=True)
    image = models.ImageField(
        upload_to=upload_image_location
    )
    thumbnail_image = models.ImageField(
        upload_to=partial(upload_image_location, thumbnail=True), 
        editable=False, blank=True
    )

    def create_thumbnail(self):
        image = Image.open(self.image.file.file)
        image.thumbnail(size=(310, 230))
        image_file = BytesIO()
        image.save(image_file, image.format)
        self.thumbnail_image.save(
            self.image.name,
            InMemoryUploadedFile(
                image_file,
                None, '',
                self.image.file.content_type,
                image.size,
                self.image.file.charset,
            ),
            save=False
        )

@receiver(models.signals.pre_save, sender=Article)
def prepare_images(sender, instance, **kwargs):
    if instance.pk:
        try:
            article = Article.objects.get(pk=instance.pk)
            old_image = article.image
            old_thumbnail_image = article.thumbnail_image
        except Article.DoesNotExist:
            return
        else:
            new_image_extension = os.path.splitext(instance.image.name)[1]
            if old_image and not old_image.name.endswith(new_image_extension):
                old_image.delete(save=False)
                old_thumbnail_image.delete(save=False)

    if not instance.thumbnail_image or not instance.image._committed:
        instance.create_thumbnail()

使用Pillow以create_thumbnail方法创建图像的缩略图。此方法可与django-storages配合使用，并将缩略图保存在自定义存储中，其名称为“ article_slug_thumbnail.jpeg”。

我的upload_image_location方法：

def upload_image_location(instance, filename, thumbnail=False):
    _, ext = os.path.splitext(filename)
    return f'articles/{instance.slug}{f"_thumbnail" if thumbnail else ""}{ext}'

Answer 3

class Profile(models.Model):
user = models.OneToOneField(User,on_delete=models.CASCADE)
image = models.ImageField(default = 'default.jpg',upload_to='profile_pics')

def __str__(self):
    return f'{self.user.username} Profile'
def save(self):
    super().save()

    img = Image.open(self.image.path)
    if img.height >300 or img.width >300:
        oputput_size = (300,300)
        img.thumbnail(oputput_size)
        img.save(self.image.path)

如何将枕头图像对象保存到Django ImageField？

3 个答案: