g_src = img_parts[0] | strip -%}
            {%- assign dim_spec = img_parts[1] | default: '' | strip -%}
            {%- assign w = '' -%}
            {%- assign h = '' -%}
            {%- if dim_spec contains 'x' and dim_spec contains '0' or dim_spec contains '1' or dim_spec contains '2' or dim_spec contains '3' or dim_spec contains '4' or dim_spec contains '5' or dim_spec contains '6' or dim_spec contains '7' or dim_spec contains '8' or dim_spec contains '9' -%}
                {%- assign dims = dim_spec