private String getImageName(DockerComposeServiceWrapper mapper, ImageConfiguration unresolvedConfig) {
        String name = mapper.getImage();
        if (name != null) {
            return name;
        } else if (unresolvedConfig.getAlias() != null && unresolvedConfig.getAlias().equals(mapper.getAlias())) {
            return unresolvedConfig.getName();
        } else {
            return null;
        }
    }
Docker Compose handler for allowing a docker-compose file to be used
to specify the docker images.
src/main/java/io/fabric8/maven/docker/config/handler/compose/DockerComposeConfigHandler.java