Django Admin model.clean() 检查上传文件的属性

Question

I have a Django model which allows an image to be uploaded, but before saving in the Django Admin, I need to verify that the uploaded image meets specific criteria for its dimensions, and show a validation error if not.

What I have so far (not much.)...

class CertificateTemplate(models.Model):
    ...
    image_file = models.FileField(
        upload_to="certificate/templates",
        help_text=_(u"We recommend a .png image of 842px by 595px"))
    ...

    def clean(self):
        print("cleaning")
        img = Image.open(self.image_file.path)
        w,h = img.size
        print(w)
        print(h)

Of course, this throws a FileNotFound error, as I assume the file hasn't actually been saved into the upload_to path at this point in the code.

Note that there's no custom form for this, since this will all be managed directly in the Django Admin pages.

How can I get the dimensions/properties of an FileField file in the model.clean() method?

I presume it will be something along the lines of using TemporaryUploadedFile?

Any help much appreciated, and am open to alternative methods/approaches for this.

Edit: in case it makes any difference, I'm on Django 2.2

Answer 1

Here what you need

def validate_image(image):
    img = Image.open(image.file)
    width, height = img.size
    # check height and width
    if "does not meet requirements":
        raise ValidationError("Error - your message")

image_file = models.ImageField('Image', upload_to=image_upload_path, validators=[validate_image])