django – 如何在保存之前使用PIL调整新上传的图像大小？

这是我的代码,它保存原始图像,不要调整大小的照片：

models.py：

class Photo(models.Model):        
    photo = models.ImageField(upload_to='photos/default/')


    def save(self):

        if not self.id and not self.photo:
            return            

        super(Photo,self).save()

        image = Image.open(self.photo)
        (width,height) = image.size

        "Max width and height 800"        
        if (800 / width < 800 / height):
            factor = 800 / height
        else:
            factor = 800 / width

        size = ( width / factor,height / factor)
        image.resize(size,Image.ANTIALIAS)
        image.save(self.photo.path)