DCMTK
Version 3.6.9
OFFIS DICOM Toolkit
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=================================== DCMTK COMPILE TIME FLAGS AND MACROS =================================== The behavior of several DCMTK tools and libraries can be modified by a number of compile time flags (macros), which are explained below. Most of these macros enable experimental or rarely needed features in DCMTK, others disable certain functions. So please, use with care! Note: CMake users simply need to add a new definition to CXXFLAGS, e.g.: CXXFLAGS=-DENABLE_DCMJPLS_INTERLEAVE_NONE && cmake [...] /path/to/dcmtk ALLOW_ILLUMINATION_OVERRIDE Affected: dcmprscu Type of modification: Activates experimental or rarely used feature Explanation: Allows the settings for Illumination and Reflected Ambient Light, which are stored in a Stored Print object, to be overridden from the print job command file. BUGGY_IMPLEMENTATION_CLASS_UID_PREFIX Affected: storescp Type of modification: Activates workaround for known bug in other product Explanation: The dcmnet module contains a workaround that allows to communicate with some buggy Storage SCUs. If the global flag dcmPeerRequiresExactUIDCopy is enabled, an illegal space padding in the Affected SOP Instance UID field of the C-STORE-RQ message is retained in the corresponding C-STORE-RSP message. When this preprocessor macro is defined, it should contain the prefix of an implementation class UID of an implementation known to exhibit the buggy behavior. The workaround is then activated in storescp whenever a Storage SCU with the given implementation class UID root connects. DCMTK_BUILD_DATE Affected: dcmdata Type of modification: Toolkit customization Explanation: When this macro is defined (typically in config/Makefile.def), the given date is used instead of the official DCMTK release data. This allows for example to specify the date of a current development snapshot. DCMTK_BUILD_IN_PROGRESS Affected: all modules Type of modification: Toolkit customization Explanation: When building DLLs, exported symbols must be marked differently if the DLL itself is built or when the DLL shall be used. This macro is defined when the DCMTK gets built and should not be defined when user code that just uses the DCMTK is built. Based on this, the correct annotation gets selected and is used in the code. There should be no valid reasons to define this macro yourself since this is done automatically by the build system. DCMTK_ENABLE_ACR_NEMA_DATASET_PRESENT_COMPATIBILITY Affected: dcmnet Type of modification: Toolkit customization Explanation: In DCMTK releases before 3.6.8, some tools incorrectly compare DataSetType for equality with DIMSE_DATASET_PRESENT, instead of checking whether DataSetType is different from DIMSE_DATASET_NULL. These tools will fail if a different value than 0x0001 is used for this constant. See DCMTK issue #1045. The DICOM standard, on the other hand, recommends the value 0x0102 if backwards compatibility with ACR-NEMA is desired. If this is important, compile with this macro enabled. DCMTK_ENABLE_OUTDATED_DCMTK_WORKAROUND Affected: dcmnet Type of modification: Activates feature Explanation: If compiled with this macro, some workarounds for backwards compatibility with very old DCMTK releases dating back to 1994-95 are re-enabled. DCMTK_ENABLE_ICONV_PASSTHROUGH Affected: oficonv Type of modification: Activates feature Explanation: If compiled with this macro, the oficonv library will simply copy input to output during a character set conversion if input and output encoding are the same. This is more efficient, but means that invalid byte sequences in the source will remain undetected and copied to the target, whereas the default behavior would detect this and stop the conversion. It is also incompatible with the behavior of the GNU iconv library. In DCMTK 3.6.8, this feature was always enabled. DCMTK_ENABLE_STRICT_HUFFMAN_TABLE_CHECK Affected: dcmjpeg Type of modification: Activates feature Explanation: DCMTK releases up to 3.6.6 contained a relatively strict check for the validity of Huffman tables for DC components in the JPEG decoder. At least one JPEG implementation produces valid JPEG images that fail this test (see DCMTK issue #1018). The test has, therefore, been disabled. This macro re-enables the old behavior. DCMTK_ENABLE_UNSAFE_VSNPRINTF Affected: ofstd Type of modification: Activates feature Explanation: DCMTK requires the snprintf(3)/vsnprintf(3) function, which was introduced with C99 and may not be supported by very old compilers. As a "last resort", an implementation internally using sprintf/vsprintf can be enabled with this macro, which allows the user to compile DCMTK on platforms that do not have the new functions. The implementation allocates a buffer that is 1 kByte larger than the "size" parameter, formats the string into that buffer, and then uses strlcpy() to copy the formatted string into the output buffer, truncating if necessary. This will work in most cases, since few snprintf calls should overrun their buffer by more than 1K, but it can be easily abused by a malicious attacker to cause a buffer overrun. Therefore, this implementation should only be used as a "last resort" and we strongly advise against using it in production code. DCMTK_GUI Affected: all modules Type of modification: Activates experimental or rarely used feature Explanation: When this macro is defined, DCMTK re-assigns the standard output and error streams maintained by ofConsole to string streams. This will allow a GUI based application to extract the messages and either present them to the user or store them in a log file. See comments in ofstd/include/dcmtk/ofstd/ofconsol.h. DCMTK_LOG4CPLUS_AVOID_WIN32_FLS Affected: oflog Type of modification: Disables feature Explanation: Starting with release 3.6.5, DCMTK uses fiber local storage instead of thread local storage in the oflog module on Windows to store thread-specific information. This has the advantage that a callback can be (and is) registered that automatically cleans up the memory when a thread ends. The old behavior can be re-activated with this macro. This may be necessary when an application wants to use multiple fibers within a single thread. In that case, before ending a thread, dcmtk::log4cplus::threadCleanup() should be called by the user code in order to clean-up oflog's thread local storage. DCMTK_MERGE_STDERR_TO_STDOUT Affected: dcmdata Type of modification: Activates feature Explanation: DCMTK releases up to 3.6.6 redirected the stderr stream to stdout on Windows to make it easier to pipe the output of the command line tools to "more". With the introduction of the ability to write DICOM files to stdout, this feature has been disabled as debug output will otherwise get mixed into the DICOM file. The old behavior can be re-activated by compiling with this macro. In this case, DICOM files should never be written to stdout as this will be unreliable. DCMTK_USE_OFLOG_LOGGER_IN_STUB Affected: ofstd Type of modification: Selects implementation variant Explanation: The command line application stub defined in ofstub.h that calls another command line tool and forwards the command line option by default prints error messages and warnings to stderr. When compiling with this macro defined, the messages are printed to the oflog logger instead, which, however, increases the executable size and slows down execution a bit. DCMTK_USE_UNIX_SOCKET_QUEUE Affected: ofstd Type of modification: Selects implementation variant Explanation: The implementation of message queues for inter-process communication in DCMTK can either use Windows mailslots, Posix message queues, System V message queues, or a solution based on Unix Domain sockets and a separate thread that handles incoming connections in the message queue server. When this macro is defined, the implementation based on Unix Domain sockets is preferred when possible (i.e. Unix Domain sockets and threads are available). This macro can be used on platforms where the use of the other IPC mechanisms causes problems, e.g. because of platform specific limitations to the number of queues permitted system-wide. DICOMDIR_WITHOUT_BACKUP Affected: dcmdata Type of modification: Disables feature Explanation: By default, DCMTK creates a backup of an existing DICOMDIR (using the name DICOMDIR.$$$) when a DcmDicomDir object is written to file. The creation of the backup can be disabled with this macro. DISABLE_COMPRESSION_EXTENSION Affected: dcmqrdb Type of modification: Disables feature Explanation: Disables the support of compression (various transfer syntaxes) in dcmqrdb, a feature which is still experimental. DISABLE_FF_JPEG_BITSTREAM_PADDING Affected: dcmjpeg, dcmjpls (dcmjpls only up to DCMTK 3.6.4) Type of modification: Disables feature Explanation: Starting with release 3.6.2, DCMTK pads JPEG and JPEG-LS bitstreams that have odd length with an "extended" end of image (EOI) marker, writing "ff/ff/d9" instead of adding a zero byte after the EOI marker, i.e. writing "ff/d9/00". The old behavior can be restored by defining this macro. In the dcmjpls module, the macro has been replaced by a codec parameter that can be set at runtime starting with DCMTK 3.6.5. DISABLE_NAGLE_ALGORITHM Affected: dcmnet Type of modification: Disables feature Explanation: By default, DCMTK does not disable the so-called Nagle algorithm, which allows for improving the efficiency of TCP/IP networks by reducing the number of packets that need to be sent over the network. When compiled with this macro, the Nagle algorithm is disabled for each DICOM transport connection. This was the default in earlier versions of the DCMTK but does not seem to be appropriate anymore for most modern operating systems. The default behavior can be changed by setting the environment variable TCP_NODELAY accordingly (see config/docs/envvars.txt or /usr/local/share/doc/dcmtk-<VERSION>/envvars.txt). DISABLE_PORT_PERMISSION_CHECK Affected: most/all network server tools Type of modification: Disables feature Explanation: By default, most network server tools (e.g. storescp) check for sufficient privileges to listen on the specified port (if geteuid() is available on the particular system). For examples, on Unix systems listening on port < 1024 usually requires root privileges. However, the port permission check might prevent the tool from being run on such ports on systems with fine-grained permission control (e.g. Linux). Therefore, this check can be disabled using this flag. DISABLE_RECV_TIMEOUT This macro is not supported anymore since the timeout for the recv() function is now configurable at runtime. See global variable dcmSocketReceiveTimeout. DISABLE_SEND_TIMEOUT This macro is not supported anymore since the timeout for the send() function is now configurable at runtime. See global variable dcmSocketSendTimeout. DONT_DISABLE_NAGLE_ALGORITHM This macro is not supported anymore since the Nagle algorithm is no longer disabled by default. See DISABLE_NAGLE_ALGORITHM for details. DOXYGEN Affected: everything Type of modification: Hides complexity from Doxygen Explanation: Doxygen is unable to parse some complex statements correctly and it is sometimes sufficient to provide documentation for the basic functionality instead of documenting every detail. This macro is defined when creating the documentation with Doxygen and should NEVER be defined when compiling DCMTK with a C/C++ compiler. NOTE: Doxygen is still unable to expand some macros correctly (e.g. HAVE_WINDOWS_H). Using this macro at the appropriate locations could be a solution for this problem. DCM_DICT_DEFAULT Affected: dcmdata Type of modification: Activates feature Explanation: This macro controls which kind of default dictionary is loaded on startup. Three settings are possible: 0: Do not load any default dictionary on startup 1: Load builtin dictionary on startup 2: Load external (i.e. file-based) dictionary on startup See dcmtk/dcmdata/docs/datadict.txt for further details. DCM_DICT_USE_DCMDICTPATH Affected: dcmdata Type of modification: Activates feature Explanation: This macro controls whether DCMDICTPATH environment variable is evaluated on startup. If so, any dictionary files provided through DCMDICTPATH will be loaded on startup. See dcmtk/dcmdata/docs/datadict.txt for further details. ENABLE_DCMJPLS_INTERLEAVE_NONE Affected: dcmjpls Type of modification: Enables feature Explanation: Re-enables the option for uninterleaved encoding (--interleave-none) in the JPEG-LS encoder on command line and library level. This option was removed after DCMTK 3.6.5 since it may in certain cases (color image with BitsStored > 12) create compressed images that are correct but cannot be decoded by the JPEG-LS library due to a known bug (DCMTK issue #892). The option will be re-enabled permanently once DCMTK has been ported to CharLS 2.x, another branch of the JPEG-LS library that requires a C++14 compiler, however. ENABLE_CSTDIO_BASED_ATOF_IMPLEMENTATION Affected: all modules Type of modification: Activates feature Explanation: The implementation of OFStandard::atof() by default uses iostreams on Posix platforms and cstdio on Windows, because on Windows this is much faster. This macro can be defined to enable the cstdio based implementation on all platforms. THIS IS STRONGLY DISCOURAGED because the cstdio based implementation suffers from a race condition that may occur if a different thread changes the locale while OFStandard::atof() is running. In this case, the result returned by OFStandard::atof() may be incorrect. The Windows version is NOT affected by this race condition because Windows offers a propietary version of sscanf where the locale can be passed explicitly. This macro is mutually exclusive with ENABLE_OLD_OFSTD_ATOF_IMPLEMENTATION and ENABLE_IOSTREAM_BASED_ATOF_IMPLEMENTATION. ENABLE_CSTDIO_BASED_FTOA_IMPLEMENTATION Affected: all modules Type of modification: Activates feature Explanation: The implementation of OFStandard::ftoa() by default uses iostreams on Posix platforms and cstdio on Windows, because on Windows this is much faster. This macro can be defined to enable the cstdio based implementation on all platforms. The implementation contains code that addresses changes to the locale, so this is not an issue in ftoa. This macro is mutually exclusive with ENABLE_OLD_OFSTD_FTOA_IMPLEMENTATION and ENABLE_IOSTREAM_BASED_FTOA_IMPLEMENTATION. ENABLE_IOSTREAM_BASED_ATOF_IMPLEMENTATION Affected: all modules Type of modification: Activates feature Explanation: The implementation of OFStandard::atof() by default uses iostreams on Posix platforms and cstdio on Windows, because on Windows this is much faster. This macro can be defined to enable the iostream based implementation on all platforms. This macro is mutually exclusive with ENABLE_OLD_OFSTD_ATOF_IMPLEMENTATION and ENABLE_CSTDIO_BASED_ATOF_IMPLEMENTATION. ENABLE_IOSTREAM_BASED_FTOA_IMPLEMENTATION Affected: all modules Type of modification: Activates feature Explanation: The implementation of OFStandard::ftoa() by default uses iostreams on Posix platforms and cstdio on Windows, because on Windows this is much faster. This macro can be defined to enable the iostream based implementation on all platforms. This macro is mutually exclusive with ENABLE_OLD_OFSTD_FTOA_IMPLEMENTATION and ENABLE_CSTDIO_BASED_FTOA_IMPLEMENTATION. ENABLE_OLD_OFSTD_ATOF_IMPLEMENTATION Affected: all modules Type of modification: Re-activates behavior of earlier DCMTK releases Explanation: DCMTK provides an implementation of atof() in class OFStandard that converts strings to double numbers in a locale-independent manner, whereas std::atof(), std::strtod() etc. depend on the global setting of the locale for the current process and may expect a decimal point character other than the period character. The implementation used in DCMTK 3.5.2 to 3.6.8 was found to produce rounding errors in certain cases and has thus been replaced by an iostream-based implementation. This macro re-activates the old version. ENABLE_OLD_OFSTD_FTOA_IMPLEMENTATION Affected: all modules Type of modification: Re-activates behavior of earlier DCMTK releases Explanation: DCMTK provides an implementation of ftoa() in class OFStandard that converts double numbers to strings in a locale-independent manner, whereas sprintf(), ftoa() etc. depend on the global setting of the locale for the current process and may expect a decimal point character other than the period character. The implementation used in DCMTK 3.5.2 to 3.6.8 was found to produce rounding errors in certain cases and has thus been replaced by an iostream-based implementation. This macro re-activates the old version. EXPERIMENTAL_READ_FROM_FILE Affected: dump2dcm Type of modification: Activates experimental or rarely used feature Explanation: When this macro is defined, the relatively new function createValueFromTempFile() is used for reading large binary data files. LOCK_IMAGE_FILES Affected: dcmpstat, dcmqrdb Type of modification: Activates experimental or rarely used feature Explanation: When this macro is defined, the DICOM image file to be send or received/created is locked exclusively. LOG4CPLUS_DISABLE_xxx (where xxx is one of TRACE, DEBUG, INFO, WARN, ERROR and FATAL) Affected: oflog Type of modification: Disables feature Explanation: When one of these macros is defined, all log message of this type and lower are disabled and optimized away. NO_GET_SUPPORT Affected: dcmqrdb Type of modification: Disables feature Explanation: Disables the experimental C-GET support in dcmqrdb. NO_PATIENTSTUDYONLY_SUPPORT Affected: dcmqrdb Type of modification: Disables feature Explanation: Disables support for the Patient/Study Only Query/Retrieve Model in dcmqrdb. OFCONDITION_IMPLICIT_BOOL_CONVERSION Affected: ofstd Type of modification: Activates experimental or rarely used feature Explanation: Activates an implicit conversion from OFCondition to OFBool, i.e. operator OFBool(). Implicit conversion might not always be a good idea since it can hide unwanted constructs. Therefore, this operator is disabled by default. ON_THE_FLY_COMPRESSION Affected: storescu Type of modification: Activates experimental or rarely used feature Explanation: When this macro is defined, the storescu tries to compress or decompress the DICOM image to be sent (if required) depending on the negotiated transfer syntax. OLD_USER_INFO_SUB_ITEM_ORDER Affected: dcmnet Type of modification: Activates experimental or rarely used feature Explanation: Prior DCMTK releases did not encode A-ASSOCIATE user information sub-items in ascending order, i.e. they sent 55H followed by 54H and 56H. This behavior has been "legalized" by DICOM CP-280, but is known to create problems with some other toolkits. The current DCMTK release always sends the user information sub-items in ascending order, but can be "forced" with this macro to revert to the old behavior. It should be re-activated for testing purposes only. PASTEL_COLOR_OUTPUT Affected: dcmimgle, dcmimage Type of modification: Activates experimental or rarely used feature Explanation: Activates experimental code in dcmimgle/dcmimage that renders monochrome images with pastel colors. PDV_TEST Affected: dcmnet Type of modification: Activates experimental or rarely used feature Explanation: Causes the network module to insert a false, zero-length PDV (2-byte header) into each P-DATA-PDU. PIXELSTACK_MEMORY_LEAK_WORKAROUND Affected: dcmdata Type of modification: Activates experimental or rarely used feature Explanation: On certain platforms there seems to be a memory leak in DcmDataset::chooseRepresentation(). The work-around activated by this macro should solve this issue. POISON_DEPRECATED_FEATURE_MACROS Affected: all modules Type of modification: Declares deprecated feature macros as "poisoned" Explanation: The osconfig.h file generated by DCMTK at configure time contains a number of deprecated feature macros that are neither used nor tested anymore in DCMTK and will be removed in a future version. When compiling with gcc or clang, this macro will cause the compilation of user code that relies on one of these macros to generate an error. This prevents the use of feature macros that may not be present anymore and thus unintended behavior. Unfortunately, this functionality is not available for MSVC users, since MSVC's "#pragma deprecated(NAME)" does not catch the use of a macro in an #if statement like "#ifdef NAME". PRINT_REPLACED_DICTIONARY_ENTRIES Affected: dcmdata Type of modification: Activates experimental or rarely used feature Explanation: When reading the data dictionary, duplicate entries (i.e. entries replacing an older entry in the dictionary) are reported on console if compiled with this macro. Useful for testing a new dictionary version. REJECT_FILE_IF_META_GROUP_LENGTH_ABSENT Affected: dcmdata Type of modification: Disables feature Explanation: When reading the a file that contains an incorrect meta header where meta header group length (0002,0000) is absent, DCMTK since release 3.5.4 nevertheless tries to parse the file, unless this macro is enabled, in which case the behavior up to DCMTK 3.5.3 is retained. RETAIN_ASSOCIATION Affected: dcmqrti Type of modification: Activates experimental or rarely used feature Explanation: Keeps association to remote Query SCP open after study/series/image listing. Default behavior is to open a new association for each query. REVERSE_OVERLAY_ORIGIN_ORDER Affected: dcmimgle Type of modification: Activates experimental or rarely used feature Explanation: When compiled with this macro, dcmimgle assumes that the values in Overlay Origin (60xx,0050) are in reverse order, i.e. X\Y instead of Y\X. SITE_UID_ROOT Affected: dcmdata Type of modification: Site customization Explanation: dcmdata contains a routine that generates DICOM unique identifiers (UIDs). By default, these are constructed from the OFFIS UID namespace, i.e. using the OFFIS UID Root "1.2.276.0.7230010.3". Users who prefer to let the toolkit generate UIDs from their own UID namespace should compile DCMTK with SITE_UID_ROOT defined to their own UID root. Please make sure that the resulting UIDs do not exceed the 64 characters limit! DCMTK may add a maximum of 44 characters to the UID root when generating UIDs. Therefore, the root must not be longer than 20 characters in order to avoid UID truncation. STARVIEW Affected: dcmimgle, dcmimage Type of modification: Activates experimental or rarely used feature Explanation: Enables support for old StarView 2 GUI class library from Star Division. SUPPRESS_CREATE_STAMP Affected: dcmdata Type of modification: Activates experimental or rarely used feature Explanation: When defined, suppresses the creation of a time stamp comment when re-generating dcdeftag.h and dcdictbi.cc. USE__LOCKING Affected: dcmnet Type of modification: Activates alternative implementation Explanation: Activates an alternative emulation of flock() on Win32 platforms using _locking(). This version should only be used on compilers where _get_osfhandle() is not available since it does not implement shared locks. USE_BINARY_MODE_FOR_STDOUT_ON_WINDOWS Affected: dcmdata Type of modification: Activates experimental or rarely used feature Explanation: On Windows systems, the standard output (stdout) is opened in text mode by default. Therefore, the binary output of tools like dcm2pnm to stdout does not work correctly (in contrast to Unix systems). When this preprocessor macro is defined, the binary mode is enabled for stdout. However, this causes newlines in the textual output to be converted to LF only (instead of CR LF which would be the usual translation for Windows). USE_NULL_SAFE_OFSTRING Affected: ofstd Type of modification: Activates feature Explanation: When this macro is defined, OFString(NULL) results in an empty string. If this macro is not defined, OFString(NULL) causes a NULL pointer dereference. This macro has no effect when HAVE_STL_STRING is also defined. Currently, this macro is always defined by DCMTK's Makefiles. This will change in future releases. USE_WIN32_CREATE_MUTEX Affected: ofstd Type of modification: Activates alternative implementation Explanation: Starting with DCMTK 3.6.2, the Win32 version of the OFMutex class uses critical sections instead of Win32 mutexes, because critical sections are much faster. Their only drawback is that they cannot be shared across processes. Users who want to revert to the behavior of older DCMTK releases can define this macro. USE_WIN32_READ_WRITE_LOCK_HELPER Affected: ofstd Type of modification: Re-activated behavior of earlier DCMTK releases Explanation: Starting with DCMTK 3.6.4, the Win32 version of the OFReadWriteLock class uses Slim Reader/Writer (SRW) Locks, which are available since Windows Vista, instead of the older implementation based on a Mutex, a Semaphore and a counter, because SRW locks are much faster. Users who want to revert to the behavior of older DCMTK releases can define this macro. USING_STD_NAMESPACE Affected: all modules Type of modification: Re-activated behavior of earlier DCMTK releases Explanation: DCMTK by default does not anymore pollute the default namespace by importing namespace std. Earlier releases did this to simplify compatibility with older compilers where STL classes were not consistently defined in namespace std. We now have configure macros which should care for this. If user code still relies on namespace std to be included, compile with this macro defined. WIDE_CHAR_FILE_IO_FUNCTIONS Affected: ofstd Type of modification: Activates feature Explanation: In addition to the standard file I/O functions, the OFFile class also defines the corresponding wide character functions from C99 standard. Since these functions are not yet supported by all compilers and the current implementation is Windows-specific, this feature is disabled by default. When using CMake, you can enable this macro by setting the CMake option DCMTK_WIDE_CHAR_FILE_IO_FUNCTIONS to "on". WIDE_CHAR_MAIN_FUNCTION Affected: currently not used Type of modification: Activates experimental or rarely used feature Explanation: On Windows (at least for MSVC), a different main function has to be used in order to get the command line arguments with wide character encoding (UTF-16). By defining this flag, the macro DCMTK_MAIN_FUNCTION expands to wmain() instead of main(). When using CMake, you can enable this macro by setting the CMake option DCMTK_WIDE_CHAR_MAIN_FUNCTION to "on". Usually, WIDE_CHAR_FILE_IO_FUNCTIONS should also be enabled. WIDE_CHAR_XML_PARSER Affected: ofstd Type of modification: Activates experimental or rarely used feature Explanation: The XML parser that is part of the DCMTK also supports a wide character API, at least on Windows systems. By defining this macro, the type "wchar_t" is used for character strings instead of "char". Please note, however, that some DCMTK tools and classes have not yet been adapted for the wide character API of the parser, e.g. cda2dcm and the underlying class DcmEncapsulatedDocument. This is also the reason why there is no CMake option yet. WRITE_VERY_LARGE_CHUNKS Affected: dcmdata Type of modification: Re-activated behavior of earlier DCMTK releases Explanation: On Windows (at least for some versions of MSVC), calls to fwrite() for more than 67,076,095 bytes (a bit less than 64 MByte) fail if we're writing to a network share. See MSDN KB899149. As a workaround, we always write in chunks of 32M which should hardly negatively affect performance. This macro enables the behavior of earlier DCMTK releases, i.e. to always call fwrite with as much data as possible, which is known not to work correctly on Win32 but might offer very minor performance benefits on other platforms. ZLIB_ENCODE_RFC1950_HEADER Affected: dcmdata Type of modification: Activates experimental or rarely used feature Explanation: When this macro is defined, the deflated ZLIB format is created instead of the deflated bitstream format (i.e. RFC 1950 instead of RFC 1951). Please note that the resulting bitstream is not DICOM compliant. So, use only for testing, and use with care!