Django custom validation in model form for imagefield (max file size etc.)

Question

I have a modelform that has an imagefield called 'banner' and I am trying to validate the file size and dimesions and provide an error if the image is too large.

Here is the models.py:

class Server(models.Model):
    id = models.AutoField("ID", primary_key=True, editable=False)
    servername = models.CharField("Server Name", max_length=20)
    ip = models.CharField("IP Address", max_length=50)
    port = models.CharField("Port", max_length=5, default='25565')
    banner = models.ImageField("Banner", upload_to='banners', max_length=100)
    description = models.TextField("Description", blank=True, max_length=3000)
    rank = models.IntegerField(default=0)
    votes = models.IntegerField(default=0)
    website = models.URLField("Website URL", max_length=200, blank=True)
    user = models.ForeignKey(User)
    motd = models.CharField("MOTD", max_length=150, default='n/a')
    playersonline = models.CharField("Online Players", max_length=7, default='n/a')
    online = models.BooleanField("Online", default=False)
    sponsored = models.BooleanField("Sponsored", default=False)
    lastquery = models.DateTimeField('Last Queried', auto_now=True)
    slugurl = models.SlugField("SlugURL", max_length=50)
    def __unicode__(self):
        return "%s (%s:%s)" % (self.servername, self.ip, self.port)

Here is the forms.py with the custom validation:

class AddServer(ModelForm):
    class Meta:
        model = Server
        fields = ('servername', 'ip', 'port', 'website', 'description', 'banner')

     # Add some custom validation to our image field
    def clean_image(self):
        image = self.cleaned_data.get('banner', False)
        if image:
            if image._size > 1*1024*1024:
                raise ValidationError("Image file too large ( maximum 1mb )")
            if image._height > 60 or image._width > 468:
                raise ValidationError("Image dimensions too large ( maximum 468x60 pixels )")
            return image
        else:
            raise ValidationError("Couldn't read uploaded image")

From what I have read this should work but the image just uploads regardless of the size.

Am I doing something wrong or is there a better way to go about doing this?

Answer 1

Just answering here for the record:

The poster didn't check the form.cleaned_data(), which means that clean_xxx validation didn't get run.

Answer 2

The name of method should be clean_<field name>, in this case clean_banner.

For future reference I will place a snippet of code that I used in one recent project (names must be adapted to work with OP code):

from PIL import Image
from django.utils.translation import ugettext as _

def clean_photo(self):
    image = self.cleaned_data.get('photo', False)

    if image:
        img = Image.open(image)
        w, h = img.size

        #validate dimensions
        max_width = max_height = 500
        if w > max_width or h > max_height:
            raise forms.ValidationError(
                _('Please use an image that is smaller or equal to '
                  '%s x %s pixels.' % (max_width, max_height)))

        #validate content type
        main, sub = image.content_type.split('/')
        if not (main == 'image' and sub.lower() in ['jpeg', 'pjpeg', 'png', 'jpg']):
            raise forms.ValidationError(_('Please use a JPEG or PNG image.'))

        #validate file size
        if len(image) > (1 * 1024 * 1024):
            raise forms.ValidationError(_('Image file too large ( maximum 1mb )'))
    else:
        raise forms.ValidationError(_("Couldn't read uploaded image"))
    return image