EnumAdapter.java

public interface EnumAdapter<EnumType, ReturnType> {
    ReturnType getValue(EnumType enumType);
}

ImageFormat.java

public enum ImageFormat {
    DEFAULT,
    PNG,
    PNG8,
    PNG24,
    PNG32,
    JPG,
    BMP,
    GIF,
    TIFF,
    EMF,
    PS,
    PDF,
    SVG,
    SVGZ,
    UNKNOWN;
}

ImageFormatEnumAdapter.java

public class ImageFormatEnumAdapter implements EnumAdapter<ImageFormat, String> {

    public String getValue(final ImageFormat imageFormat) {
        switch (imageFormat) {
            case DEFAULT: return "";
            case PNG: return "png";
            case PNG8: return "png8";
            case PNG24: return "png24";
            case PNG32: return "png32";
            case JPG: return "jpg";
            case BMP: return "bmp";
            case GIF: return "gif";
            case TIFF: return "tiff";
            case EMF: return "emf";
            case PS: return "ps";
            case PDF: return "pdf";
            case SVG: return "svg";
            case SVGZ: return "svgz";
            default: return null;
        }
    }
}