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dcm2img: Convert DICOM image to standard image format

# SYNOPSIS

    dcm2img [options] dcmfile-in [bitmap-out]

# DESCRIPTION

The dcm2img utility reads a DICOM image, converts the pixel data according to the selected image processing options and writes back an image in one the following general purpose image formats: BMP, PGM/PPM, PNG, TIFF, JPEG, or JPEG-LS. This utility supports uncompressed as well as JPEG, JPEG-LS and RLE compressed DICOM images.

# PARAMETERS

    dcmfile-in  DICOM input filename to be converted ("-" for stdin)

    bitmap-out  output filename to be written (default: 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

      -ll   --log-level  [l]evel: string constant
              (fatal, error, warn, info, debug, trace)
              use level l for the logger

      -lc   --log-config  [f]ilename: string
              use config file f for the logger

## 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

## image processing options

    frame selection:

      +F    --frame  [n]umber: integer
              select specified frame (default: 1)

      +Fr   --frame-range  [n]umber [c]ount: integer
              select c frames beginning with frame n

      +Fa   --all-frames
              select all frames

    rotation:

      +Rl   --rotate-left
              rotate image left (-90 degrees)

      +Rr   --rotate-right
              rotate image right (+90 degrees)

      +Rtd  --rotate-top-down
              rotate image top-down (180 degrees)

    flipping:

      +Lh   --flip-horizontally
              flip image horizontally

      +Lv   --flip-vertically
              flip image vertically

      +Lhv  --flip-both-axes
              flip image horizontally and vertically

    scaling:

      +a    --recognize-aspect
              recognize pixel aspect ratio when scaling (default)

      -a    --ignore-aspect
              ignore pixel aspect ratio when scaling

      +i    --interpolate  [n]umber of algorithm: integer
              use interpolation when scaling (1..4, default: 1)

      -i    --no-interpolation
              no interpolation when scaling

      -S    --no-scaling
              no scaling, ignore pixel aspect ratio (default)

      +Sxf  --scale-x-factor  [f]actor: float
              scale x axis by factor, auto-compute y axis

      +Syf  --scale-y-factor  [f]actor: float
              scale y axis by factor, auto-compute x axis

      +Sxv  --scale-x-size  [n]umber: integer
              scale x axis to n pixels, auto-compute y axis

      +Syv  --scale-y-size  [n]umber: integer
              scale y axis to n pixels, auto-compute x axis

    color space conversion (JPEG compressed images only):

      +cp   --conv-photometric
              convert if YCbCr photometric interpretation (default)

      +cl   --conv-lossy
              convert YCbCr to RGB if lossy JPEG

      +cg   --conv-guess
              convert to RGB if YCbCr is guessed by library

      +cgl  --conv-guess-lossy
              convert to RGB if lossy JPEG and YCbCr is
              guessed by the underlying JPEG library

      +ca   --conv-always
              always convert YCbCr to RGB

      +cn   --conv-never
              never convert color space

    bits stored:

      +bs  --bits-stored-fix
             correct inconsistent bits stored value (default)

      # If the value of BitsStored in the compressed bitstream is smaller
      # than the value in the DICOM dataset, update the value in the dataset
      # (JPEG compressed images only)

      -bs  --bits-stored-keep
             preserve inconsistent bits stored value

      # Keep the value of BitsStored even if inconsistent with the
      # compressed bitstream. This may help in correctly decoding some
      # defective images JPEG compressed images only)

    workaround options for incorrect encodings (JPEG compressed images only):

      +w6   --workaround-pred6
              enable workaround for JPEG lossless images
              with overflow in predictor 6

      # DICOM images with 16 bits/pixel have been observed "in the wild"
      # that are compressed with lossless JPEG and need special handling
      # because the encoder produced an 16-bit integer overflow in predictor
      # 6, which needs to be compensated (reproduced) during decompression.
      # This flag enables a correct decompression of such faulty images, but
      # at the same time will cause an incorrect decompression of correctly
      # compressed images. Use with care.

      +wi   --workaround-incpl
              enable workaround for incomplete JPEG data

      # This option causes dcm2img to ignore incomplete JPEG data
      # at the end of a compressed fragment and to start decompressing
      # the next frame from the next fragment (if any). This permits
      # images with incomplete JPEG data to be decoded.

      +wc   --workaround-cornell
              enable workaround for 16-bit JPEG lossless
              Cornell images with Huffman table overflow

      # One of the first open-source implementations of lossless JPEG
      # compression, the "Cornell" library, has a well-known bug that leads
      # to invalid values in the Huffmann table when images with 16 bit/sample
      # are compressed. This flag enables a workaround that permits such
      # images to be decoded correctly.

    modality LUT transformation:

      -M    --no-modality
              ignore stored modality LUT transformation

      +M    --use-modality
              use modality LUT transformation (default)

    VOI LUT transformation:

      -W    --no-windowing
              no VOI windowing (default)

      +Wi   --use-window  [n]umber: integer
              use the n-th VOI window from image file

      +Wl   --use-voi-lut  [n]umber: integer
              use the n-th VOI look up table from image file

      +Wm   --min-max-window
              compute VOI window using min-max algorithm

      +Wn   --min-max-window-n
              compute VOI window using min-max algorithm,
              ignoring extreme values

      +Wr   --roi-min-max-window  [l]eft [t]op [w]idth [h]eight: integer
              compute ROI window using min-max algorithm,
              region of interest is specified by l,t,w,h

      +Wh   --histogram-window  [n]umber: integer
              compute VOI window using Histogram algorithm,
              ignoring n percent

      +Ww   --set-window  [c]enter [w]idth: float
              compute VOI window using center c and width w

      +Wfl  --linear-function
              set VOI LUT function to LINEAR

      +Wfs  --sigmoid-function
              set VOI LUT function to SIGMOID

    presentation LUT transformation:

      +Pid  --identity-shape
              set presentation LUT shape to IDENTITY

      +Piv  --inverse-shape
              set presentation LUT shape to INVERSE

      +Pod  --lin-od-shape
              set presentation LUT shape to LIN OD

    overlay:

      -O    --no-overlays
              do not display overlays

      +O    --display-overlay  [n]umber: integer
              display overlay n (0..16, 0=all, default: +O 0)

      +Omr  --ovl-replace
              use overlay mode "Replace"
              (default for Graphic overlays)

      +Omt  --ovl-threshold
              use overlay mode "Threshold Replace"

      +Omc  --ovl-complement
              use overlay mode "Complement"

      +Omv  --ovl-invert
              use overlay mode "Invert Bitmap"

      +Omi  --ovl-roi
              use overlay mode "Region of Interest"
              (default for ROI overlays)

      +Osf  --set-foreground  [d]ensity: float
              set overlay foreground density (0..1, default: 1)

      +Ost  --set-threshold  [d]ensity: float
              set overlay threshold density (0..1, default: 0.5)

    display LUT transformation:

      +Dm   --monitor-file  [f]ilename: string
              calibrate output according to monitor characteristics
              defined in f

      +Dp   --printer-file  [f]ilename: string
              calibrate output according to printer characteristics
              defined in f

      +Da   --ambient-light  [a]mbient light: float
              ambient light value (cd/m^2, default: file f)

      +Di   --illumination  [i]llumination: float
              illumination value (cd/m^2, default: file f)

      +Dn   --min-density  [m]inimum optical density: float
              Dmin value (default: off, only with +Dp)

      +Dx   --max-density  [m]aximum optical density: float
              Dmax value (default: off, only with +Dp)

      +Dg   --gsd-function
              use GSDF for calibration (default for +Dm/+Dp)

      +Dc   --cielab-function
              use CIELAB function for calibration

    compatibility:

      +Ma   --accept-acr-nema
              accept ACR-NEMA images without photometric
              interpretation

      +Mp   --accept-palettes
              accept incorrect palette attribute tags
              (0028,111x) and (0028,121x)

      +Mc   --check-lut-depth
              check 3rd value of the LUT descriptor, compare
              with expected bit depth based on LUT data

      +Mm   --ignore-mlut-depth
              ignore 3rd value of the modality LUT descriptor,
              determine bits per table entry automatically

      +Mv   --ignore-vlut-depth
              ignore 3rd value of the VOI LUT descriptor,
              determine bits per table entry automatically

    TIFF format:

      +Tl   --compr-lzw
              LZW compression (default)

      +Tr   --compr-rle
              RLE compression

      +Tn   --compr-none
              uncompressed

      +Pd   --predictor-default
              no LZW predictor (default)

      +Pn   --predictor-none
              LZW predictor 1 (no prediction)

      +Ph   --predictor-horz
              LZW predictor 2 (horizontal differencing)

      +Rs   --rows-per-strip  [r]ows: integer (default: 0)
              rows per strip, default 8K per strip

    PNG format:

      +il   --interlace
              create interlaced file (default)

      -il   --nointerlace
              create non-interlaced file

      +mf   --meta-file
              create PNG file meta information (default)

      -mf   --meta-none
              no PNG file meta information

    JPEG format:

      +Jq   --compr-quality  [q]uality: integer (0..100, default: 90)
              quality value for compression (in percent)

      +Js4  --sample-444
              4:4:4 sampling (no subsampling)

      +Js2  --sample-422
              4:2:2 subsampling (horizontal subsampling of
              chroma components, default)

      +Js1  --sample-411
              4:1:1 subsampling (horizontal and vertical
              subsampling of chroma components)

    JPEG-LS format:

      +Trl  --rendered-lossless
              lossless compression of rendered image (default)

      +Tll  --true-lossless
              lossless compression of raw image

      +f8   --force-8-bit
              force output bit depth to 8 bits
              (not with --true-lossless)

    other transformations:

      +G    --grayscale
              convert color image to grayscale (monochrome)

      +P    --change-polarity
              change polarity (invert pixel output)

      +C    --clip-region  [l]eft [t]op [w]idth [h]eight: integer
              clip image region (l, t, w, h)

## output options

    general:

      -im   --image-info
              print image details (requires verbose mode)

      -o    --no-output
              do not create any output (useful with -im)

    filename generation (only with --frame-range or --all-frames):

      +Fc   --use-frame-counter
              use 0-based counter for filenames (default)

      +Fn   --use-frame-number
              use absolute frame number for filenames

    image format:

      +oa   --write-auto
              determine file format from filename extension
              (default for files)

      # If the output filename contains no extension or an
      # unknown/unsupported one, a warning is printed and a BMP file
      # is written (see --write-bmp).

      +op   --write-raw-pnm
              write 8-bit binary PGM/PPM

      +opb  --write-8-bit-pnm
              write 8-bit ASCII PGM/PPM (default for stdout)

      +opw  --write-16-bit-pnm
              write 16-bit ASCII PGM/PPM

      +opn  --write-n-bit-pnm  [n]umber: integer
              write n-bit ASCII PGM/PPM (1..32)

      +ob   --write-bmp
              write 8-bit (monochrome) or 24-bit (color) BMP

      +obp  --write-8-bit-bmp
              write 8-bit palette BMP (monochrome only)

      +obt  --write-24-bit-bmp
              write 24-bit truecolor BMP

      +obr  --write-32-bit-bmp
              write 32-bit truecolor BMP

      +ot   --write-tiff
              write 8-bit (monochrome) or 24-bit (color) TIFF

      +on   --write-png
              write 8-bit (monochrome) or 24-bit (color) PNG

      +on2  --write-16-bit-png
              write 16-bit (monochrome) or 48-bit (color) PNG

      +oj   --write-jpeg
              write 8-bit lossy JPEG (baseline)

      +ol   --write-jpls
              write JPEG-LS

# NOTES

The following preferred interpolation algorithms can be selected using the --interpolate option:

- 1 = free scaling algorithm with interpolation from pbmplus toolkit
- 2 = free scaling algorithm with interpolation from c't magazine
- 3 = magnification algorithm with bilinear interpolation from Eduard Stanescu
- 4 = magnification algorithm with bicubic interpolation from Eduard Stanescu

The --write-tiff option is only available when DCMTK has been configured and compiled with support for the external libtiff TIFF library. The availability of the TIFF compression options depends on the libtiff configuration.

The --write-png option is only available when DCMTK has been configured and compiled with support for the external libpng PNG library. Option --interlace enables progressive image view while loading the PNG file. Only a few applications take care of the meta info (TEXT) in a PNG file.

# TRANSFER SYNTAXES

dcm2img 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
    JPEGLSLosslessTransferSyntax                   1.2.840.10008.1.2.4.80
    JPEGLSLossyTransferSyntax                      1.2.840.10008.1.2.4.81
    JPEGProcess10_12TransferSyntax                 1.2.840.10008.1.2.4.55
    JPEGProcess14SV1TransferSyntax                 1.2.840.10008.1.2.4.70
    JPEGProcess14TransferSyntax                    1.2.840.10008.1.2.4.57
    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
    RLELosslessTransferSyntax                      1.2.840.10008.1.2.5

(*) if compiled with zlib support enabled

# LOGGING

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

The dcm2img 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 behavior 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.

# FILES

<datadir>/camera.lut - sample characteristics file of a camera
<datadir>/monitor.lut - sample characteristics file of a monitor
<datadir>/printer.lut - sample characteristics file of a printer
<datadir>/scanner.lut - sample characteristics file of a scanner

# SEE ALSO

img2dcm(1)

# COPYRIGHT

Copyright (C) 2001-2025 by OFFIS e.V., Escherweg 2, 26121 Oldenburg, Germany.

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