Sorl-thumbnail generates black square instead of image

Question

I'm developing my project inside a Vagrant VM, the software version I'm using is:

• Ubuntu 12.04
• Django 1.6
• Sorl Thumbnail 11.12
• Pillow 2.5.3

I have some pictures in the path /var/www/django/my_project/media/icons and I have a model with an ImageField pointing to that path.

I have also THUMBNAIL_DEBUG = True in my settings.py

In my template I use thumbnail like:

{% thumbnail category.image "20" as im %}
    <img src="{{ im.url }}"></img>
{% empty %}
    {% thumbnail "png/no_image.png" "20" as im %}  # Thumbnail add the rest of the path to media
        <img id="no_image" alt="" src="{{ im.url }}" />
    {% endthumbnail%}
{% endthumbnail %}

There are some objects with image and some others without it and both shows just a black square instead of the image.

• Does anyone knows why is this happening ? I use Sorl-Thumbnail in many projects and never had this issue

I've tried to reset the full database, I used python manage.py thumbnail clear and python manage.py thumbnail cleanup

I've installed: libjpeg62 libjpeg62-dev zlib1g-dev

no_image.png is an image (red cross) not an empty image

• Am I missing any library or dependency ?

I'm lost because as I said I've worked with Sorl-thumbnail in other projects, and never saw anything like this.

Any help would be much appreciated

---

Edit

Here are some images I'm trying to display:

( I have png and jpg libraries working on Pillow )

And this is what I see in all cases:

Edit2

The problem is with the background. When I upload a png image with transparent background sorl converts the image to jpg and set the background to black...

• Is there any way to keep the transparent background or avoid conversion ?
• Is possible to set the background to white ?

I tried with:

THUMBNAIL_COLORSPACE = None
THUMBNAIL_PRESERVE_FORMAT = True

but didn't work

Answer 1

Finally solved !

To solve the issue with the black background:

• I updated sorl-thumbnail to 12.2
• Added this 2 lines to settings.py:
  • THUMBNAIL_COLORSPACE = None
  • THUMBNAIL_PRESERVE_FORMAT = True
    
    
• Restart thumbnail database with python manage.py thumbnail clear_delete_all