Returns default values for the get image form

def _get_form_defaults(self):
        """Returns default values for the get image form"""

        return {
            'response_format': 'html',
            'bbox': self.service.full_extent,
            'size': '400,400',
            'dpi': 200,
            'image_projection': pyproj.Proj(str(self.service.projection)),
            'bbox_projection': pyproj.Proj(str(self.service.projection)),
            'image_format': 'png',
            'transparent': True
        }