Django：使用PIL，Amazon S3和Boto调整图像大小并上传

Question

I'm trying to figure out the best way to take a user uploaded image, resize it, and store the original image as well as the resized image on Amazon S3.

I'm running Django 1.5, using PIL to resize the image, and using Boto to handle uploading the image file to S3. Right now I've got it to work by uploading the original image to S3, using PIL to open the image using the S3 path and resize it, and then saving the resized version to S3, however this doesn't seem to be the most efficient way to do this.

I'm wondering if there's a way to resize the image before uploading to S3 using the user-uploaded image itself (been having trouble getting PIL to open the image file itself), and whether this would be faster than the way I've set things up now. I can't seem to find an answer to this, either in the PIL documentation or anywhere else. I should mention that I don't want to just use a third party app to handle this, as part of my goal is to learn and understand fundamentally what is going on.

Is there a more efficient way to do this than what I've currently set up? A general explanation of what is happening at each step and why it makes the most sense to set things up that way would be ideal.

I should also mention that it seems to take much longer to upload the image to S3 than when I was just storing the image on my server. Is there a normal lag when uploading to S3 or is there potentially something in how things are set up that could be slowing down the S3 uploads?

Answer 1

I have an architecture consisting of a Django + Tastypie in Heroku and the image wharehouse in S3. What I do when a user uploads a photo from the frontend (written in JS), is resize the photo to a certain size (600 x 600 max size) always mantaining the aspect ratio. I'll paste the code to do this (it works).

views.py:

class UploadView(FormView):
    form_class = OriginalForm
    def form_valid(self, form):
        original = form.save()
        if  original.image_width > 280 and original.image_height > 281:
            if original.image_width > 600 or original.image_height > 600:
                original.resize((600, 600))
                if not original.image:
                    return self.success(self.request, form, None, errors = 'Error while uploading the image')
                original.save()
                up = UserProfile.objects.get(user = request.user.pk)
                #Save the images to s3
                s3 = S3Custom()
                new_image = s3.upload_file(original.image.path, 'avatar')
                #Save the s3 image path, as string, in the user profile
                up.avatar = new_image
                up.save
        else:
            return self.success(self.request, form, None, errors = 'The image is too small')       
        return self.success(self.request, form, original)

Here what I do is checking if the image is larger than 280 x 281 (the crop square, in the frontend, has that size), and also check if one of the sides of the image is larger than 600px. If that's the case, I call the (custom) method resize, of my Original class...

models.py:

class Original(models.Model):
    def upload_image(self, filename):
        return u'avatar/{name}.{ext}'.format(            
            name = uuid.uuid4().hex,
            ext  = os.path.splitext(filename)[1].strip('.')
        )

    def __unicode__(self):
        return unicode(self.image)

    owner = models.ForeignKey('people.UserProfile')
    image = models.ImageField(upload_to = upload_image, width_field  = 'image_width', height_field = 'image_height')
    image_width = models.PositiveIntegerField(editable = False, default = 0)
    image_height = models.PositiveIntegerField(editable = False, default = 0)  

    def resize(self, size):
        if self.image is None or self.image_width is None or self.image_height is None:
            print 'Cannot resize None things'
        else:
            IMG_TYPE = os.path.splitext(self.image.name)[1].strip('.')
            if IMG_TYPE == 'jpeg':
                PIL_TYPE = 'jpeg'
                FILE_EXTENSION = 'jpeg'
            elif IMG_TYPE == 'jpg':
                PIL_TYPE = 'jpeg'
                FILE_EXTENSION = 'jpeg'
            elif IMG_TYPE == 'png':
                PIL_TYPE = 'png'
                FILE_EXTENSION = 'png'
            elif IMG_TYPE == 'gif':
                PIL_TYPE = 'gif'
                FILE_EXTENSION = 'gif'
            else:
                print 'Not a valid format'
                self.image = None
                return
            #Open the image from the ImageField and save the path
            original_path = self.image.path
            fp = open(self.image.path, 'rb')
            im = Image.open(StringIO(fp.read()))
            #Resize the image
            im.thumbnail(size, Image.ANTIALIAS)
            #Save the image
            temp_handle = StringIO()
            im.save(temp_handle, PIL_TYPE)
            temp_handle.seek(0)
            #Save image to a SimpleUploadedFile which can be saved into ImageField
            suf = SimpleUploadedFile(os.path.split(self.image.name)[-1], temp_handle.read(), content_type=IMG_TYPE)
            #Save SimpleUploadedFile into image field
            self.image.save('%s.%s' % (os.path.splitext(suf.name)[0],FILE_EXTENSION), suf, save=False)
            #Delete the original image
            fp.close()
            os.remove(original_path)
            #Save other fields
            self.image_width = im.size[0]
            self.image_height = im.size[1]
        return

The last thing you need is a "library" containing custom s3 methods:

class S3Custom(object):
    conn = S3Connection(settings.AWS_ACCESS_KEY_ID, settings.AWS_SECRET_ACCESS_KEY)
    b = Bucket(conn, settings.AWS_STORAGE_BUCKET_NAME)
    k = Key(b)
    def upload_file(self, ruta, prefix):
        try:           
            self.k.key = '%s/%s' % (prefix, os.path.split(ruta)[-1])
            self.k.set_contents_from_filename(ruta)
            self.k.make_public()
        except Exception, e:
            print e
        return '%s%s' % (settings.S3_URL, self.k.key)

You should have AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, AWS_STORAGE_BUCKET_NAME, S3_URL in your settings file.