|o||MR images are required to have BitsAllocated=16.|
|o||NM Images can only be encoded with MONOCHROME2 or PALETTE COLOR photometric interpretation but not with RGB or YBR_FULL (which effectively prevents compression).|
|o||Hardcopy Color images must have RGB color model which is a problem if lossy compression is to be performed.|
With version DCMTK 3.5.4 a new encoder for truely lossless JPEG compression was added (--true-lossless). Compared to the old (--pseudo-lossless) encoder, that creates slightly lossy images caused from internal color space conversions, windowing etc., there are a some issues to consider:
|o||Only source images with Bits Allocated 8 or 16 are supported|
|o||Options for color space conversions, windowing or pixel scaling are ignored or overriden|
|o||Photometric Interpretations YBR_FULL_422, YBR_PARTIAL_422, YBR_PARTIAL_420, YBR_ICT, YBR_RCT are not supported|
|o||The encoder changes automatically Planar Configuration from 1 to 0 if necessary|
|o||The compression ratio can be lower than in --pseudo-lossless mode|
In order to be on the safe side, the Lossy Compression Flag is always set to 01 and a new SOP instance UID is assigned (by default) for the old pseudo-lossless encoder. The output of the old and new lossless encoder can also be distinguished by the Derivation Description in the resulting DICOM image, which contains the term Lossless JPEG compression for the new and Pseudo-Lossless JPEG compression for the old encoder.
dcmcjpeg supports the following transfer syntaxes for input (dcmfile-in):
LittleEndianImplicitTransferSyntax 1.2.840.10008.1.2 LittleEndianExplicitTransferSyntax 1.2.840.10008.1.2.1 DeflatedExplicitVRLittleEndianTransferSyntax 1.2.840.10008.1.2.1.99 (*) BigEndianExplicitTransferSyntax 1.2.840.10008.1.2.2 JPEGProcess1TransferSyntax 1.2.840.10008.1.2.4.50 JPEGProcess2_4TransferSyntax 1.2.840.10008.1.2.4.51 JPEGProcess6_8TransferSyntax 1.2.840.10008.1.2.4.53 JPEGProcess10_12TransferSyntax 1.2.840.10008.1.2.4.55 JPEGProcess14TransferSyntax 1.2.840.10008.1.2.4.57 JPEGProcess14SV1TransferSyntax 1.2.840.10008.1.2.4.70
(*) if compiled with zlib support enabled
dcmcjpeg supports the following transfer syntaxes for output (dcmfile-out):
JPEGProcess1TransferSyntax 1.2.840.10008.1.2.4.50 JPEGProcess2_4TransferSyntax 1.2.840.10008.1.2.4.51 JPEGProcess6_8TransferSyntax 1.2.840.10008.1.2.4.53 JPEGProcess10_12TransferSyntax 1.2.840.10008.1.2.4.55 JPEGProcess14TransferSyntax 1.2.840.10008.1.2.4.57 JPEGProcess14SV1TransferSyntax 1.2.840.10008.1.2.4.70
The level of logging output of the various command line tools and underlying libraries can be specified by the user. By default, only errors and warnings are written to the standard error stream. Using option --verbose also informational messages like processing details are reported. Option --debug can be used to get more details on the internal activity, e.g. for debugging purposes. Other logging levels can be selected using option --log-level. In --quiet mode only fatal errors are reported. In such very severe error events, the application will usually terminate. For more details on the different logging levels, see documentation of module oflog.
In case the logging output should be written to file (optionally with logfile rotation), to syslog (Unix) or the event log (Windows) option --log-config can be used. This configuration file also allows for directing only certain messages to a particular output stream and for filtering certain messages based on the module or application where they are generated. An example configuration file is provided in <etcdir>/logger.cfg).
All command line tools use the following notation for parameters: square brackets enclose optional values (0-1), three trailing dots indicate that multiple values are allowed (1-n), a combination of both means 0 to n values.
Command line options are distinguished from parameters by a leading + or - sign, respectively. Usually, order and position of command line options are arbitrary (i.e. they can appear anywhere). However, if options are mutually exclusive the rightmost appearance is used. This behaviour conforms to the standard evaluation rules of common Unix shells.
In addition, one or more command files can be specified using an @ sign as a prefix to the filename (e.g. @command.txt). Such a command argument is replaced by the content of the corresponding text file (multiple whitespaces are treated as a single separator unless they appear between two quotation marks) prior to any further evaluation. Please note that a command file cannot contain another command file. This simple but effective approach allows to summarize common combinations of options/parameters and avoids longish and confusing command lines (an example is provided in file <datadir>/dumppat.txt).
The dcmcjpeg utility will attempt to load DICOM data dictionaries specified in the DCMDICTPATH environment variable. By default, i.e. if the DCMDICTPATH environment variable is not set, the file <datadir>/dicom.dic will be loaded unless the dictionary is built into the application (default for Windows).
The default behaviour should be preferred and the DCMDICTPATH environment variable only used when alternative data dictionaries are required. The DCMDICTPATH environment variable has the same format as the Unix shell PATH variable in that a colon (:) separates entries. On Windows systems, a semicolon (;) is used as a separator. The data dictionary code will attempt to load each file specified in the DCMDICTPATH environment variable. It is an error if no data dictionary can be loaded.
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|Version 3.6.0||DCMCJPEG (1)||6 Jan 2011|