Plone helper

gistfile1.txt

    def url(self, image, width=None, height=None):
        """Generate a scaled image url from the given values """
        if width is None:
          width = image.width
        if height is None:
          height = image.height
        scales = image.restrictedTraverse('@@images')
        scaled_image = scales.scale(
            'image',
            width=width,
            height=height,
            direction='down',
            quality=85
        )
        return scaled_image.absolute_url()