Django Pillow, save image as jpeg does not seem to work - django

Question

Goodmorning,
I'm using Pillow to resize and save an image within a Django model called Post. The image is retrieved from the imagefield, get's a check to see if it is RGB or not, if not the image is converted to RGB.
Finally, I'm creating a thumbnail from the original image and try to save this in the MEDIA_ROOT.
Even though the image get's uploaded, it doesn't seem to convert the image to jpeg.
I followed the tutorial here Django 2+ edit images with Pillow and I'm trying to fit it to my needs.
What am I missing here?
models.py
import os
from django.core.validators import RegexValidator
from django.db import models
from django.utils import timezone
from PIL import Image
from django.conf import settings
from django.db.models.signals import post_save
class Post(models.Model):
# Custom validators
title_validator_specialchar = RegexValidator(regex=r'^[\s*\d*a-zA-Z]{5,60}$', message="The title can't contain any special characters")
category = models.ForeignKey('Category',default=1, on_delete=models.SET_NULL, null=True)
type = models.CharField(max_length=20)
title = models.CharField(max_length=200, validators=[title_validator_specialchar])
content = models.TextField(max_length=2000)
image = models.ImageField(upload_to='%Y/%m/%d/', blank=True)
created_at = models.DateTimeField(editable=False)
updated_at = models.DateTimeField(default=timezone.now)
def save(self, *args, **kwargs):
#On save, update timestamp date created
if not self.id:
self.created_at = timezone.now()
self.updated_at = timezone.now()
return super(Post, self).save(*args, **kwargs)
def __str__(self):
return self.title
def resize_image(instance, **kwargs):
if instance.image:
# we are opening image with Pillow
img = Image.open(instance.image)
# convert image to RGB
if img.mode not in ('L', 'RGB'):
img = img.convert('RGB')
# img.size is tuple with values (width, height)
if img.size[0] > 320 or img.size[1] > 640:
# Using thumbnail to resize image but keep aspect ratio
img.thumbnail((320, 640), Image.ANTIALIAS)
# saving to original place
# instance.image.name is in %Y/%m/%d/<name> format
output = os.path.join(settings.MEDIA_ROOT, instance.image.name)
img.save(output, "JPEG")
# Connect the signal with our model
post_save.connect(resize_image, Post)

Answer 1

A signal handler receives the sender as the first argument, which in case of the post_save signal is the model class, not the model instance.
So the argument instance of resize_image() should be named sender and does not contains what you want. Here is how you get the actual instance:
def resize_image(sender, **kwargs):
instance = kwargs.get('instance')
if instance and instance.image:
...

Answer 2

Since I couldn't find what I needed to get this to work, I decided to use django-imagekit.
I'm using the ProcessedImageField and the ResizeToFill processor on my model;
models.py
image = ProcessedImageField(upload_to='%Y/%m/%d/', processors=[ResizeToFill(384, 216)], format='JPEG', options={'quality': 60}, blank=True)

Answer 3

This happens beacuse You explicitly call img to save in the mediaroot but instance.image stays still. So django will save that image also. So I think You have to change the instance.image attribute rather than calling img to save. For that you have to use django InMemorUploadedFile
import io
from django.core.files.uploadedfile import InMemoryUploadedFile
import sys
if instance.image:
# we are opening image with Pillow
img = Image.open(instance.image)
# convert image to RGB
if img.mode not in ('L', 'RGB'):
img = img.convert('RGB')
# img.size is tuple with values (width, height)
if img.size[0] > 320 or img.size[1] > 640:
# Using thumbnail to resize image but keep aspect ratio
img.thumbnail((320, 640), Image.ANTIALIAS)
# saving to original place by changing instance.image. django will save it
#automatically in mediaroot
img_io = io.BytesIO()
img.save(img_io, "JPEG")
instance.image = InMemoryUploadedFile(img_io, 'ImageField', 'image.jpeg',
'image/jpeg',sys.getsizeof(img_io), None )
we can't pass the Image object directly to inastance.image because it raises an error.
so we have to convert img to InMemoryUploadedFile object.