I normally like to write code myself instead of installing some large script just to do one task for me. There were a few scripts out there that could create thumbnails, but I wanted something simple and wouldn’t use most of those features. Plus, I wanted to know how to use the Python Image Library with Django 1.0 and learn on my own how to take an uploaded picture and create a few thumbnails of them.

After searching for a while I was able to piece some things together to get something working. In my model I added these two functions.

def thumbnailed(self, file, width, height):
    from django.core.files.base import ContentFile
    from StringIO import StringIO
    import Image
        size = width, height
        tmp_file = StringIO()
        im = Image.open(StringIO(file.read()))
        format = im.format # since new im won't have format
        if format == "gif" or format == "GIF":
            im = im.convert("RGB")
        im.thumbnail(size, Image.ANTIALIAS)
        if format == "gif" or format == "GIF":
            im = im.convert("P", dither=Image.NONE, palette=Image.ADAPTIVE)
        im.save(tmp_file, format, quality=95)
    except IOError:
        return None
    return ContentFile(tmp_file.getvalue())

Using StringIO I was able to create a temporary file in memory to hold the thumbnail data and return it where it would later be passed to django. I was trying to create 3 thumbnails which presented another problem: django was obliterating the uploaded file and the data in my temp files when I was saving. So I figured out how to get around that, but there may be better ways.

def create_thumbnails(self, file):
    pic = self.thumbnailed(file, 160, 400)
    if pic is not None:
        self.picture.save(file.name, pic, save=False)
    # Django's InMemoryUploadedFile uses StringIO
    # This will reset it to be ready to use again
    thumb = self.thumbnailed(file, 288, 96)
    if thumb is not None:
        self.thumbnail.save(file.name, thumb, save=False)
    # Django's InMemoryUploadedFile uses StringIO
    # This will reset it to be ready to use again
    tiny = self.thumbnailed(file, 144, 48)
    if tiny is not None:
        self.tiny_image.save(file.name, tiny, save=False)

The model has picture, thumbnail, and tiny_image as ImageFields and create_thumbnails was originally called from the view and passed the uploaded file from request.FILES.

There was a lot of trial and error trying to get this together, so I hope it helps someone get past that.

Updated July 10, 2009

I added a condition to check if the image is a gif. If it is, it is converted so that the thumnails will look much better than they would without converting them. I also set the quality to 95 so that all images will have the best possible thumbnails.

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