使用 Pillow 在图像上传 Django 2 上调整大小并创建缩略图

Question

I am trying to resize an image on upload and also create a thumbnail out of the same resized image. I previously was able to resize the image without issues, however, when I tried adding in the thumbnail feature I was unable to get it working. I have looked at all the other related questions and all of them are either outdated or haven't worked in my case.

models.py

class Project(models.Model):
    cover_image=models.ImageField(max_length=150, upload_to='project-covers/', default='Default.png', null=True)
    thumbnail=models.ImageField(max_length=150, upload_to='project-thumbnails/', null=True)

      def save(self, *args, **kwargs):
        # pdb.set_trace()
        if self.cover_image:
            fname = self.title + '_cover.'
            tname = self.title + '_thumbnail.'
            self.resizeUploadedImage(fname)
            self.createThumbnail(tname)
        super(Project, self).save(*args, **

    def resizeUploadedImage(self, fname):
        '''Resize the image being uploaded.'''
        try:
            im = Image.open(self.cover_image)
            if im.width > IMAGE_SIZE[0] or im.heght > IMAGE_SIZE[1]:
                im.resize(IMAGE_SIZE, Image.ANTIALIAS)
                image_io = BytesIO()
                im.save(image_io, im.format)
                # pdb.set_trace()
                fname = fname + im.format
                self.cover_image.save(fname, ContentFile(image_io.read(), False))
                im.close()
                image_io.close()
        except IOError as e:
            print("Could not resize image for", self.image)
            print(e)

    def createThumbnail(self, fname):
        '''Create thumbnail of the image.'''
        try:
            if self.thumbnail is None:
                im = Image.open(self.cover_image)
                im.thumbnail(THUMB_SIZE)
                image_io = BytesIO()
                im.save(image_io, im.format)
                fname = fname + im.format
                self.thumbnail.save(fname, ContentFile(image_io.getvalue(), False))
                im.close()
        except IOError as e:
            print('Could not create a thumbnail for', self.image)
            print(e)

Originally I was using the resizeUploadedImage and createThumbnail methods and was successful with the resizing however the thumbnail was always empty on my admin page and db. Before I had 'editable=False' on the thumbnail as I wanted it to be created automatically behind the scenes. I thought that might be preventing the change so I took it out but it didn't change the results.

Then I tried moving both into the save method (as I had previously run into issues when I moved my resize outside the save) but it still doesn't work properly.

I see on several documents that it's best to put the super() call at the end of the save method, but when I do that I get

 UNIQUE constraint failed: projects_project.id 

How can I create a thumbnail out of the cover_image and save it to the thumbnail field?

PS While running ./manage.py test projects it seems to be actually saving files to my disk which I thought wasn't supposed to happen so I assume its some kind of issue with my Pillow code. I end up with '1_cover.PNG', '1Project0_cover.PNG', '1Project1_cover.PNG', '2_cover.PNG' etc, etc, etc counting up to 9 even though my setuptestdata only has 'Project 1'.

PPS I read somewhere that it's better to use Pillow's thumbnail function for resizing as it'll keep the aspect ratio whereas resize won't. Does anyone have any insight on this?

Answer 1

from PIL import Image
def save(self):
    super().save()
    img = Image.open(self.cover_image.path)
    if img.height > 250 or img.width > 250:
    output_size = (250, 250)
    img.thumbnail(output_size)
    img.save(self.cover_image.path)

try this way with the size you wanted instead of 250