@register.simple_tag
def thumbnail(image_url, width, height, upscale=True, quality=95, left=.5,
              top=.5, padding=False, padding_color="#fff"):

    if not image_url:
        return ""
    try:
        from PIL import Image, ImageFile, ImageOps
    except ImportError:
        return ""

    image_url = unquote(str(image_url)).split("?")[0]
    if image_url.startswith(settings.MEDIA_URL):
        image_url = image_url.replace(settings.MEDIA_URL, "", 1)
    image_dir, image_name = os.path.split(image_url)
    image_prefix, image_ext = os.path.splitext(image_name)
    filetype = {".png": "PNG", ".gif": "GIF"}.get(image_ext, "JPEG")
    thumb_name = "%s-%sx%s" % (image_prefix, width, height)
    if not upscale:
        thumb_name += "-no-upscale"
    if left != .5 or top != .5:
        left = min(1, max(0, left))
        top = min(1, max(0, top))
        thumb_name = "%s-%sx%s" % (thumb_name, left, top)
    thumb_name += "-padded-%s" % padding_color if padding else ""
    thumb_name = "%s%s" % (thumb_name, image_ext)

    # `image_name` is used here for the directory path, as each image
    # requires its own sub-directory using its own name - this is so
    # we can consistently delete all thumbnails for an individual
    # image, which is something we do in filebrowser when a new image
    # is written, allowing us to purge any previously generated
    # thumbnails that may match a new image name.
    thumb_dir = os.path.join(settings.MEDIA_ROOT, image_dir,
                             settings.THUMBNAILS_DIR_NAME, image_name)
    if not os.path.exists(thumb_dir):
        try:
            os.makedirs(thumb_dir)
        except OSError:
            pass

    thumb_path = os.path.join(thumb_dir, thumb_name)
    thumb_url = "%s/%s/%s" % (settings.THUMBNAILS_DIR_NAME,
                              quote(image_name.encode("utf-8")),
                              quote(thumb_name.encode("utf-8")))
    image_url_path = os.path.dirname(image_url)
    if image_url_path:
        thumb_url = "%s/%s" % (image_url_path, thumb_url)

    try:
        thumb_exists = os.path.exists(thumb_path)
    except UnicodeEncodeError:
        # The image that was saved to a filesystem with utf-8 support,
        # but somehow the locale has changed and the filesystem does not
        # support utf-8.
        from mezzanine.core.exceptions import FileSystemEncodingChanged
        raise FileSystemEncodingChanged()
    if thumb_exists:
        # Thumbnail exists, don't generate it.
        return thumb_url
    elif not default_storage.exists(image_url):
        # Requested image does not exist, just return its URL.
        return image_url

    f = default_storage.open(image_url)
    try:
        image = Image.open(f)
    except:
        # Invalid image format.
        return image_url

    image_info = image.info
    to_width = int(width)
    to_height = int(height)
    from_width = image.size[0]
    from_height = image.size[1]

    if not upscale:
        to_width = min(to_width, from_width)
        to_height = min(to_height, from_height)

    # Set dimensions.
    if to_width == 0:
        to_width = from_width * to_height // from_height
    elif to_height == 0:
        to_height = from_height * to_width // from_width
    if image.mode not in ("P", "L", "RGBA"):
        try:
            image = image.convert("RGBA")
        except:
            return image_url
    # Required for progressive jpgs.
    ImageFile.MAXBLOCK = 2 * (max(image.size) ** 2)

    # Padding.
    if padding and to_width and to_height:
        from_ratio = float(from_width) / from_height
        to_ratio = float(to_width) / to_height
        pad_size = None
        if to_ratio < from_ratio:
            pad_height = int(to_height * (float(from_width) / to_width))
            pad_size = (from_width, pad_height)
            pad_top = (pad_height - from_height) // 2
            pad_left = 0
        elif to_ratio > from_ratio:
            pad_width = int(to_width * (float(from_height) / to_height))
            pad_size = (pad_width, from_height)
            pad_top = 0
            pad_left = (pad_width - from_width) // 2
        if pad_size is not None:
            pad_container = Image.new("RGBA", pad_size, padding_color)
            pad_container.paste(image, (pad_left, pad_top))
            image = pad_container

    # Create the thumbnail.
    to_size = (to_width, to_height)
    to_pos = (left, top)
    try:
        image = ImageOps.fit(image, to_size, Image.ANTIALIAS, 0, to_pos)
        image = image.save(thumb_path, filetype, quality=quality, **image_info)
        # Push a remote copy of the thumbnail if MEDIA_URL is
        # absolute.
        if "://" in settings.MEDIA_URL:
            with open(thumb_path, "rb") as f:
                default_storage.save(thumb_url, File(f))
    except Exception:
        # If an error occurred, a corrupted image may have been saved,
        # so remove it, otherwise the check for it existing will just
        # return the corrupted image next time it's requested.
        try:
            os.remove(thumb_path)
        except Exception:
            pass
        return image_url
    return thumb_url
Given the URL to an image, resizes the image using the given width
dataset/ETHPy150Open stephenmcd/mezzanine/mezzanine/core/templatetags/mezzanine_tags.py/thumbnail