api_update_blog_view.py

from blog.api.serializers import BlogPostUpdateSerializer

# Response: https://gist.github.com/mitchtabian/32507e93c530aa5949bc08d795ba66df
# Url: https://<your-domain>/api/blog/<slug>/update
# Headers: Authorization: Token <token>
@api_view(['PUT',])
@permission_classes((IsAuthenticated,))
def api_update_blog_view(request, slug):

	try:
		blog_post = BlogPost.objects.get(slug=slug)
	except BlogPost.DoesNotExist:
		return Response(status=status.HTTP_404_NOT_FOUND)

	user = request.user
	if blog_post.author != user:
		return Response({'response':"You don't have permission to edit that."}) 
		
	if request.method == 'PUT':
		serializer = BlogPostUpdateSerializer(blog_post, data=request.data, partial=True)
		data = {}
		if serializer.is_valid():
			serializer.save()
			data['response'] = UPDATE_SUCCESS
			data['pk'] = blog_post.pk
			data['title'] = blog_post.title
			data['body'] = blog_post.body
			data['slug'] = blog_post.slug
			data['date_updated'] = blog_post.date_updated
			image_url = str(request.build_absolute_uri(blog_post.image.url))
			if "?" in image_url:
				image_url = image_url[:image_url.rfind("?")]
			data['image'] = image_url
			data['username'] = blog_post.author.username
			return Response(data=data)
		return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

BlogPostUpdateSerialzier.py

import cv2
import sys
import os
from django.conf import settings
from django.core.files.storage import default_storage
from django.core.files.storage import FileSystemStorage
IMAGE_SIZE_MAX_BYTES = 1024 * 1024 * 2 # 2MB
MIN_TITLE_LENGTH = 5
MIN_BODY_LENGTH = 50

class BlogPostUpdateSerializer(serializers.ModelSerializer):

	class Meta:
		model = BlogPost
		fields = ['title', 'body', 'image']

	def validate(self, blog_post):
		try:
			title = blog_post['title']
			if len(title) < MIN_TITLE_LENGTH:
				raise serializers.ValidationError({"response": "Enter a title longer than " + str(MIN_TITLE_LENGTH) + " characters."})
			
			body = blog_post['body']
			if len(body) < MIN_BODY_LENGTH:
				raise serializers.ValidationError({"response": "Enter a body longer than " + str(MIN_BODY_LENGTH) + " characters."})
			
			image = blog_post['image']
			url = os.path.join(settings.TEMP , str(image))
			storage = FileSystemStorage(location=url)

			with storage.open('', 'wb+') as destination:
				for chunk in image.chunks():
					destination.write(chunk)
				destination.close()

			if sys.getsizeof(image.file) > IMAGE_SIZE_MAX_BYTES:
				os.remove(url)
				raise serializers.ValidationError({"response": "That image is too large. Images must be less than 3 MB. Try a different image."})

			img = cv2.imread(url)
			dimensions = img.shape # gives: (height, width, ?)
			
			aspect_ratio = dimensions[1] / dimensions[0] # divide w / h
			if aspect_ratio < 1:
				os.remove(url)
				raise serializers.ValidationError({"response": "Image height must not exceed image width. Try a different image."})

			os.remove(url)
		except KeyError:
			pass
		return blog_post

settings.py

TEMP = os.path.join(BASE_DIR, 'temp')