Django/PIL - 在上传图片时保存缩略图版本

Question

Django/PIL - 在上传图片时保存缩略图版本

djangoimagethumbnailspython-imaging-library

24

这是我的forms.py：

class UploadImageForm(forms.ModelForm):
    class Meta:
        model = UserImages
        fields = ['photo']

这是我的models.py文件：

class UserImages(models.Model):
    user = models.ForeignKey(User)
    photo = models.ImageField(upload_to=get_file_path)

这是我的观点：

def uploadImageView(request):
    if request.method == 'POST':
        form = UploadImageForm(request.POST, request.FILES)
        if form.is_valid():
            instance = form.save(commit=False)
            instance.user = request.user
            instance.save()
            return redirect('/')
    else:
        form = UploadImageForm()

    return render(request, 'uploadImagePage.html', {'uploadImageForm': form})

但这只是保存上传的图像。我如何同时保存缩略图？缩略图的文件名与原图完全相同，只是在文件名后面加上单词“thumbnail”。

我阅读的教程说可以这样做：

im = Image.open(infile)
im.thumbnail(size, Image.ANTIALIAS)

我想获取一个缩略图，但在我的情况下，图像甚至还没有保存。

- SilentDev

7个回答

17

为了实现这个，你应该在当前的 UserImages 模型中添加一个新的 ImageField 来保存缩略图，然后重写 save 方法，在完整图片保存后创建并保存缩略图。

我从我的一个项目中调整了下面的代码片段，它可以完美地实现你的需求。

from cStringIO import StringIO
import os

from django.db import models
from django.core.files.base import ContentFile
from django.core.files.storage import default_storage as storage

from PIL import Image

# Thumbnail size tuple defined in an app-specific settings module - e.g. (400, 400)
from app.settings import THUMB_SIZE

class Photo(models.Model):
    """
    Photo model with automatically generated thumbnail.
    """
    photo = models.ImageField(upload_to='photos')
    thumbnail = models.ImageField(upload_to='thumbs', editable=False)

    def save(self, *args, **kwargs):
        """
        Make and save the thumbnail for the photo here.
        """
        super(Photo, self).save(*args, **kwargs)
        if not self.make_thumbnail():
            raise Exception('Could not create thumbnail - is the file type valid?')

    def make_thumbnail(self):
        """
        Create and save the thumbnail for the photo (simple resize with PIL).
        """
        fh = storage.open(self.photo.name, 'r')
        try:
            image = Image.open(fh)
        except:
            return False

        image.thumbnail(THUMB_SIZE, Image.ANTIALIAS)
        fh.close()

        # Path to save to, name, and extension
        thumb_name, thumb_extension = os.path.splitext(self.photo.name)
        thumb_extension = thumb_extension.lower()

        thumb_filename = thumb_name + '_thumb' + thumb_extension

        if thumb_extension in ['.jpg', '.jpeg']:
            FTYPE = 'JPEG'
        elif thumb_extension == '.gif':
            FTYPE = 'GIF'
        elif thumb_extension == '.png':
            FTYPE = 'PNG'
        else:
            return False    # Unrecognized file type

        # Save thumbnail to in-memory file as StringIO
        temp_thumb = StringIO()
        image.save(temp_thumb, FTYPE)
        temp_thumb.seek(0)

        # Load a ContentFile into the thumbnail field so it gets saved
        self.thumbnail.save(thumb_filename, ContentFile(temp_thumb.read()), save=True)
        temp_thumb.close()

        return True

- xjtian

3

在make_thumbnail中抛出异常而不是返回False会更好，这样你就可以知道异常的确切原因，而不是得到一个通用的异常信息。 - stupidbodo

1

如果此记录的非图像字段被更新，编辑时是否会调用make_thumbnail方法？ - user3750325

我在你的回复基础上进行了构建，真的帮了我很多。从一个 bug 跳到另一个 bug，我开始怀疑自己的理智。我甚至想着拿一加仑汽油点燃我的电脑。 - coredumped0x

2

另一种解决方案是正确的，但在实现为个人资料图片时会失败。可以安全地假设个人资料将不仅仅是一张图片和缩略图。如果更新任何其他字段而个人资料图片未更新，则可能遇到几个不同的问题。为了避免这种情况，必须实现原始文件名与更新后返回的文件名之间的比较。如果个人资料图片未更新，则不希望保存缩略图。将类字符串设置为None，并在运行make_thumbnail之前进行比较。

import os.path
from PIL import Image
from io import BytesIO
from django.core.files.base import ContentFile
from .my_app_settings import THUMB_SIZE    

class Photo(models.Model):
    photo = models.ImageField(upload_to='photos')
    thumbnail = models.ImageField(upload_to='thumbs', editable=False)
    
    # Class string added to store original name of photo
    original_photo_name = None 

    # When the form is initialized save the original photo name
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.original_photo_name = self.photo.name

    def save(self, *args, **kwargs):
        # This checks if the photo was updated or not before saving a thumbnail
        if self.original_photo_name != self.photo.name: 
            if not self.make_thumbnail():
                # set to a default thumbnail
                raise Exception('Could not create thumbnail - is the file type valid?')

        super(Photo, self).save(*args, **kwargs)

    def make_thumbnail(self):

        image = Image.open(self.photo)
        image.thumbnail(THUMB_SIZE, Image.ANTIALIAS)

        thumb_name, thumb_extension = os.path.splitext(self.photo.name)
        thumb_extension = thumb_extension.lower()

        thumb_filename = thumb_name + '_thumb' + thumb_extension

        if thumb_extension in ['.jpg', '.jpeg']:
            FTYPE = 'JPEG'
        elif thumb_extension == '.gif':
            FTYPE = 'GIF'
        elif thumb_extension == '.png':
            FTYPE = 'PNG'
        else:
            return False    # Unrecognized file type

        # Save thumbnail to in-memory file as StringIO
        temp_thumb = BytesIO()
        image.save(temp_thumb, FTYPE)
        temp_thumb.seek(0)

        # set save=False, otherwise it will run in an infinite loop
        self.thumbnail.save(thumb_filename, ContentFile(temp_thumb.read()), save=False)
        temp_thumb.close()

        return True

- Pat

2

我根据ziiiro的答案编写了它。它在Django2.2.1上运行良好。需要处理图像字段的路径以保存。

models.py

from django.db import models
from my.images import make_thumbnail


class Image(models.Model):
    image = models.ImageField(upload_to='')
    thumbnail = models.ImageField(upload_to='', editable=False)
    icon = models.ImageField(upload_to='', editable=False)

    def save(self, *args, **kwargs):
        # save for image
        super(Image, self).save(*args, **kwargs)

        make_thumbnail(self.thumbnail, self.image, (200, 200), 'thumb')
        make_thumbnail(self.icon, self.image, (100, 100), 'icon')

        # save for thumbnail and icon
        super(Image, self).save(*args, **kwargs)

my.images.py

from django.core.files.base import ContentFile
import os.path
from PIL import Image
from io import BytesIO


def make_thumbnail(dst_image_field, src_image_field, size, name_suffix, sep='_'):
    """
    make thumbnail image and field from source image field

    @example
        thumbnail(self.thumbnail, self.image, (200, 200), 'thumb')
    """
    # create thumbnail image
    image = Image.open(src_image_field)
    image.thumbnail(size, Image.ANTIALIAS)

    # build file name for dst
    dst_path, dst_ext = os.path.splitext(src_image_field.name)
    dst_ext = dst_ext.lower()
    dst_fname = dst_path + sep + name_suffix + dst_ext

    # check extension
    if dst_ext in ['.jpg', '.jpeg']:
        filetype = 'JPEG'
    elif dst_ext == '.gif':
        filetype = 'GIF'
    elif dst_ext == '.png':
        filetype = 'PNG'
    else:
        raise RuntimeError('unrecognized file type of "%s"' % dst_ext)

    # Save thumbnail to in-memory file as StringIO
    dst_bytes = BytesIO()
    image.save(dst_bytes, filetype)
    dst_bytes.seek(0)

    # set save=False, otherwise it will run in an infinite loop
    dst_image_field.save(dst_fname, ContentFile(dst_bytes.read()), save=False)
    dst_bytes.close()

- arai

这个方法在你移动基础媒体根目录之后就不再适用了，例如upload_to='my_sub_folder'。我最终得到的缩略图是在mediaroot/my_sub_folder/my_subfolder/中创建的。将dst_name, dst_ext行更新为：dst_name, dst_ext = os.path.splitext(os.path.basename(src_image_field.name))，并将dst_fname行更新为dst_fname = '{}{}{}{}'.format(dst_name, sep, name_suffix, dst_ext)，这样问题就得到了解决。 - Andy Stagg

0

如果您不想从头开始实现一个解决方案，我建议您使用一个名为sorl-thumbnail的Django应用程序。

- Luca

我会将它作为备份，但我正在寻找一种从头开始实现解决方案的方法。我不认为这应该很难，只是找不到正确的PIL / Pillow文档。 - SilentDev

0

可能您忘记保存文件了：

im.save(file + ".thumbnail", "JPEG")

请查看http://effbot.org/imagingbook/image.htm#examples

- Albert Tugushev

正确，但问题是，什么是im？如果你看我的代码，我没有指定im。我执行instance.save（和instance = form.save）。因此，我一开始就没有im，因为我无法打开文件（在你喜欢的例子中，他们首先执行im = Image.open(infile)）。我该如何打开一个未知位置的文件，因为我尚未保存它？我想同时保存图像和缩略图版本的图像。 - SilentDev

2

在保存模型实例后，您应该制作缩略图。像这样保存实例：obj = instance.save()。之后，您可以像这样获取图像实例：im = Image.open(obj.photo.path)。但最好重写类UploadImageForm的save方法并处理缩略图。 - Albert Tugushev

0

有一种超级简单的方法，

在模型中：

def upload_thumb_dir(self, filename):
        path = f'path_to_thumb.jpg'
        return path

thumb = ProcessedImageField(upload_to=upload_thumb_dir,
    processors=[ResizeToFill(192, 108)],
    max_length= 255,
    format='JPEG',
    default='preview.jpg',
    options={'quality': 80},
    null=True, blank=True
)
# ...
def save(self, *args, **kwargs):
    self.thumb = self.rawfile.file
    super(VersionPreviews, self).save(*args, **kwargs)

- Saeid Gholizade

网页内容由stack overflow 提供, 点击上面的

可以查看英文原文，
原文链接

- Badjio · Accepted Answer

基于xjtian的回答。这适用于Python 3：

import os.path
from PIL import Image
from io import BytesIO
from django.core.files.base import ContentFile
from .my_app_settings import THUMB_SIZE    

class Photo(models.Model):
    photo = models.ImageField(upload_to='photos')
    thumbnail = models.ImageField(upload_to='thumbs', editable=False)

    def save(self, *args, **kwargs):

        if not self.make_thumbnail():
            # set to a default thumbnail
            raise Exception('Could not create thumbnail - is the file type valid?')

        super(Photo, self).save(*args, **kwargs)

    def make_thumbnail(self):

        image = Image.open(self.photo)
        image.thumbnail(THUMB_SIZE, Image.ANTIALIAS)

        thumb_name, thumb_extension = os.path.splitext(self.photo.name)
        thumb_extension = thumb_extension.lower()

        thumb_filename = thumb_name + '_thumb' + thumb_extension

        if thumb_extension in ['.jpg', '.jpeg']:
            FTYPE = 'JPEG'
        elif thumb_extension == '.gif':
            FTYPE = 'GIF'
        elif thumb_extension == '.png':
            FTYPE = 'PNG'
        else:
            return False    # Unrecognized file type

        # Save thumbnail to in-memory file as StringIO
        temp_thumb = BytesIO()
        image.save(temp_thumb, FTYPE)
        temp_thumb.seek(0)

        # set save=False, otherwise it will run in an infinite loop
        self.thumbnail.save(thumb_filename, ContentFile(temp_thumb.read()), save=False)
        temp_thumb.close()

        return True