dcmconv(1)

🌸 NAME 🌸

Bestie, meet dcmconv — like, literally dcmconv(1) from OFFIS DCMTK 💅 and its whole main-character job is: Convert DICOM file encoding. No cap.

✨ SYNOPSIS ✨

The vibe check is:

dcmconv [options] dcmfile-in dcmfile-out

🦋 DESCRIPTION 🦋

The dcmconv utility reads a DICOM file (dcmfile-in), performs an encoding conversion, and writes the converted data to an output file (dcmfile-out). That's the whole assignment, and it ate. 💖

🎀 PARAMETERS 🎀

• dcmfile-in — DICOM input filename to be converted ("-" for stdin)
• dcmfile-out — DICOM output filename to write to ("-" for stdout)

👑 OPTIONS 👑

💅 general options 💅

• -h, --help — print this help text and exit
• --version — print version information and exit
• --arguments — print expanded command line arguments
• -q, --quiet — quiet mode, print no warnings and errors
• -v, --verbose — verbose mode, print processing details
• -d, --debug — debug mode, print debug information
• -l, --log-level — takes [l]evel: string constant (fatal, error, warn, info, debug, trace) and uses level l for the logger
• -l, --log-config — takes [f]ilename: string and uses config file f for the logger

Yes bestie, the original really lists -l on both of those. I’m just the messenger. 🫶

🌈 input options 🌈

🎀 input file format: 🎀

• +f, --read-file — read file format or data set (default)
• +fo, --read-file-only — read file format only
• -f, --read-dataset — read data set without file meta information

🎀 input transfer syntax: 🎀

• -t=, --read-xfer-auto — use TS recognition (default)
• -td, --read-xfer-detect — ignore TS specified in the file meta header
• -te, --read-xfer-little — read with explicit VR little endian TS
• -tb, --read-xfer-big — read with explicit VR big endian TS
• -ti, --read-xfer-implicit — read with implicit VR little endian TS

🎀 parsing of file meta information: 🎀

• +ml, --use-meta-length — use file meta information group length (default)
• -ml, --ignore-meta-length — ignore file meta information group length

🎀 parsing of odd-length attributes: 🎀

• +ao, --accept-odd-length — accept odd length attributes (default)
• +ae, --assume-even-length — assume real length is one byte larger

🎀 handling of explicit VR: 🎀

• +ev, --use-explicit-vr — use explicit VR from dataset (default)
• -ev, --ignore-explicit-vr — ignore explicit VR (prefer data dictionary)

🎀 handling of non-standard VR: 🎀

• +vr, --treat-as-unknown — treat non-standard VR as unknown (default)
• -vr, --assume-implicit — try to read with implicit VR little endian TS

🎀 handling of undefined length UN elements: 🎀

• +ui, --enable-cp246 — read undefined len UN as implicit VR (default)
• -ui, --disable-cp246 — read undefined len UN as explicit VR

🎀 handling of defined length UN elements: 🎀

• -uc, --retain-un — retain elements as UN (default)
• +uc, --convert-un — convert to real VR if known

🎀 handling of private max-length elements (implicit VR): 🎀

• -sq, --maxlength-dict — read as defined in dictionary (default)
• +sq, --maxlength-seq — read as sequence with undefined length

🎀 handling of wrong delimitation items: 🎀

• -rd, --use-delim-items — use delimitation items from dataset (default)
• +rd, --replace-wrong-delim — replace wrong sequence/item delimitation items

🎀 handling of illegal undefined length OB/OW elements: 🎀

• -oi, --illegal-obow-rej — reject dataset with illegal element (default)
• +oi, --illegal-obow-conv — convert undefined length OB/OW element to SQ

🎀 handling of VOI LUT Sequence with OW VR and explicit length: 🎀

• -vi, --illegal-voi-rej — reject dataset with illegal VOI LUT (default)
• +vi, --illegal-voi-conv — convert illegal VOI LUT to SQ

🎀 handling of explicit length pixel data for encaps. transfer syntaxes: 🎀

• -pe, --abort-expl-pixdata — abort on explicit length pixel data (default)
• +pe, --use-expl-pixdata — use explicit length pixel data

🎀 general handling of parser errors: 🎀

• +Ep, --ignore-parse-errors — try to recover from parse errors
• -Ep, --handle-parse-errors — handle parse errors and stop parsing (default)

🎀 other parsing options: 🎀

• +st, --stop-after-elem — takes [t]ag: "gggg,eeee" or dictionary name; stop parsing after the element specified by t

🎀 automatic data correction: 🎀

• +dc, --enable-correction — enable automatic data correction (default)
• -dc, --disable-correction — disable automatic data correction

🎀 bitstream format of deflated input: 🎀

• +bd, --bitstream-deflated — expect deflated bitstream (default)
• +bz, --bitstream-zlib — expect deflated zlib bitstream

🧚 processing options 🧚

🎀 specific character set: 🎀

# the following options require support from an underlying character
# encoding library (see output of --version on which one is available)

• +U8, --convert-to-utf8 — convert all element values that are affected by Specific Character Set (0008,0005) to UTF-8
• +L1, --convert-to-latin1 — convert affected element values to ISO 8859-1
• +A7, --convert-to-ascii — convert affected element values to 7-bit ASCII
• +C, --convert-to-charset — takes [c]harset: string; convert affected element values to the character set specified by the DICOM defined term c
• -Ct, --transliterate — try to approximate characters that cannot be represented through similar looking characters
• -Cd, --discard-illegal — discard characters that cannot be represented in destination character set

🎀 other processing options: 🎀

• -ig, --no-invalid-groups — remove elements with invalid group number

🍓 output options 🍓

🎀 output file format: 🎀

• +Fm, --write-new-meta-info — write file format with new meta information (default)
• +F, --write-file — write file format
• -F, --write-dataset — write data set without file meta information

🎀 output transfer syntax: 🎀

• +t=, --write-xfer-same — write with same TS as input (default)
• +te, --write-xfer-little — write with explicit VR little endian TS
• +tb, --write-xfer-big — write with explicit VR big endian TS
• +ti, --write-xfer-implicit — write with implicit VR little endian TS
• +td, --write-xfer-deflated — write with deflated explicit VR little endian TS
• +tg, --write-xfer-ge — write private GE implicit VR little endian with big endian pixel data TS (non-standard)

🎀 post-1993 value representations: 🎀

• +u, --enable-new-vr — enable support for new VRs (UN/UT) (default)
• -u, --disable-new-vr — disable support for new VRs, convert to OB

🎀 group length encoding: 🎀

• +g=, --group-length-recalc — recalculate group lengths if present (default)
• +g, --group-length-create — always write with group length elements
• -g, --group-length-remove — always write without group length elements

🎀 length encoding in sequences and items: 🎀

• +e, --length-explicit — write with explicit lengths (default)
• -e, --length-undefined — write with undefined lengths
• +eo, --write-oversized — write oversized explicit length sequences and items with undefined length (default)
• -eo, --abort-oversized — abort on oversized explicit sequences/items

🎀 data set trailing padding (not with --write-dataset): 🎀

• -p=, --padding-retain — do not change padding (default if not --write-dataset)
• -p, --padding-off — no padding (implicit if --write-dataset)
• +p, --padding-create — takes [f]ile-pad [i]tem-pad: integer; align file on multiple of f bytes and items on multiple of i bytes

🎀 deflate compression level (only with --write-xfer-deflated): 🎀

• +cl, --compression-level — takes [l]evel: integer (default: 6); 0=uncompressed, 1=fastest, 9=best compression

💻 LOGGING 💻

Okay so logging is a whole mood. 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.

🌟 COMMAND LINE 🌟

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 behavior 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 one to summarize common combinations of options/parameters and avoids longish and confusing command lines (an example is provided in file <datadir>/dumppat.txt).

🌸 ENVIRONMENT 🌸

Okay bestie, this is the part where dcmconv goes looking for its little reference books 📚 — the data dictionaries and the character set mapping tables. Listen up, because if these aren't where it expects, it's gonna be sad.

🗂️ The data dictionary hunt (DCMDICTPATH)

• DCMDICTPATH — the environment variable dcmconv checks when it wants to load DICOM data dictionaries. That's the whole vibe.

By default — like, if DCMDICTPATH isn't set at all — the file <datadir>/dicom.dic gets loaded. Unless the dictionary is built into the application (which is the default for Windows, iykyk 🪟).

Lowkey important: the default behavior should be what you prefer, fr fr. Only reach for DCMDICTPATH when you actually need alternative data dictionaries. Don't be out here setting env vars for no reason 💅

Now the format — and it's giving Unix shell PATH energy:

• Entries are separated by a colon (":") on Unix.
• On Windows systems, a semicolon (";") is the separator instead.

The data dictionary code will attempt to load each file specified in DCMDICTPATH. And heads up:

It is an error if no data dictionary can be loaded. 😭 Like, full stop. Nothing loads = bad time.

🔤 The character set mapping tables (DCMICONVPATH)

Depending on which command line options you specified, dcmconv will also attempt to load character set mapping tables. This happens when:

1. DCMTK was compiled with the oficonv library (which is the default ✨), and
2. the mapping tables are not built into the library (the default when DCMTK uses shared libraries).

So where does it look? 👀

• The mapping table files are expected in DCMTK's <datadir>.
• DCMICONVPATH — set this environment variable to point at a different location.

Plot twist: if you specify a different location, those mapping tables also replace any built-in tables. So it's not a "just add more" situation — it's a full swap. Choose wisely 🫶

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👀 SEE ALSO 👀

• dcmdump(1) — go read that one too, bestie, it's the other main character here 🎀

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©️ COPYRIGHT ©️

Copyright (C) 1994-2026 by OFFIS e.V., Escherweg 2, 26121 Oldenburg, Germany.

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And that's a wrap on dcmconv(1), bestie!! 🦋 You made it to the end, I'm so proud 😭💖 This was Version 3.7.1, dated Sat Oct 17 2026 09:34:01 — go forth, convert those DICOM files, and slay ✨👑