        std::string PngChunk::makeMetadataChunk(const std::string& metadata, MetadataId type)
        {
            std::string chunk;
            std::string rawProfile;

            switch (type) {
                case mdComment:
                    chunk = makeUtf8TxtChunk("Description", metadata, true);
                    break;
                case mdExif:
                    rawProfile = writeRawProfile(metadata, "exif");
                    chunk = makeAsciiTxtChunk("Raw profile type exif", rawProfile, true);
                    break;
                case mdIptc:
                    rawProfile = writeRawProfile(metadata, "iptc");
                    chunk = makeAsciiTxtChunk("Raw profile type iptc", rawProfile, true);
                    break;
                case mdXmp:
                    chunk = makeUtf8TxtChunk("XML:com.adobe.xmp", metadata, false);
                    break;
                case mdIccProfile:
                    break;
                case mdNone:
                    assert(false);
            }

            return chunk;

        }  // PngChunk::makeMetadataChunk
Unknown