ctrans man page

ctrans — a Computer Graphics Metafile ( CGM ) translator


ctrans [ -bell ] [ -d device ] [ -f font ] [ -lmin min ] [ -lmax max ] [ -lscale scale ] [ -movie time ] [ -outfile file ] [ -pal pal_fname ] [ -pause ] [ -quiet ] [ -record record_num ... ] [ -soft ] [ -verbose ] [ -Version ] [ -viewport llx:lly:urx:ury ] [ -wid window_id ] [ -window llx:lly:urx:ury ] [ device-specific options ]  [ - | metafile ... ]


ctrans is a metafile translator, taking metafile(s), a metafile stored in the NCAR Computer Graphics Metafile (CGM) standard, and interpreting its instructions on the device defined by the GRAPHCAP environment variable. Fonts are stroked according to specifications in the Fontcap file defined by the FONTCAP environment variable. ctrans utilizes Graphcaps by default,  see graphcap(5NCARG), while providing optional processing by user provided libraries, if that is required by the device or desired by the user. Thus, ctrans is capable of driving any device for which a Graphcap is available; with  programming modifications, ctrans can accommodate any device for which an external library of plotting routines is available.  Currently, the following Graphcap independent devices are supported: X11 under release 4 and 5, version 11 of X.

ctrans can also translate metacode into the following raster formats: a60, avs, hdf, hppcl, nrif, sun and xwd. The device specifier for these raster formats is the name of the format. For example "-d xwd" specifies translation to an xwd formatted raster file. Additionally, a clear text driver, "-d CTXT", is available on any terminal.  Not all of the aforementioned devices may be supported by your particular configuration of ctrans. For a list of supported devices see the gcaps(1NCARG) command.

ctrans will read from the standard input if no metafile name is specified or the the name specified is `-'.



Ring the bell at the end of each frame. The default is to run in silent mode. This option is not supported by all devices.

-d device

Device name. ctrans will use the Graphcap (if it exists) or the appropriate graphics library indicated by device;

If device is preceded by a UNIX directory path then ctrans will look in that directory for the specified graphcap. Otherwise ctrans searches the directory $NCARG_ROOT/lib/ncarg/graphcaps for the graphcap.

For all device specifications except X11 output is directed to standard out. In the case of X11 translation results in appropriate calls to the X11 libraries. See graphcap(5NCARG) for a description of supported devices.  See gcaps(1NCARG) for a list of devices supported by your particular configuration of ctrans.

This option overrides the GRAPHCAP environment variable.

-f fontcap

Fontcap file to be used for stroking text. When interpreting CGM TEXT command elements use fontcap as the default font for textual translation. Note: CGMs may contain textual descriptions which are not embedded in CGM TEXT elements. Hence they are not influenced by fontcap specifications. Note also that a CGM may explicitly specify a named font which may override a font provided on the command line. The environment variable FONTCAP may also be used to specify a default fontcap.

If fontcap is preceded by a UNIX directory path then ctrans will look in that directory for the specified fontcap. Otherwise ctrans searches the directory $NCARG_ROOT/lib/ncarg/fontcaps for the fontcap.

See fontcap(5NCARG) for a description of the available fontcaps. See fcap(1NCARG) for a list of the fontcaps installed on your system.

This option overrides the FONTCAP environment variable.

-lmin min

On devices which support line width scaling all lines are guaranteed to be scaled at least min times the default line width for that device. This option effectively  insures that the minimum value for the CGM element "LINE WIDTH" is min.

-lmax max

On devices which support line width scaling all lines are guaranteed to be scaled at most max times the default line width for that device. This option effectively  insures that the maximum value for the CGM element "LINE WIDTH" is max. The results of setting max less then min are undefined.

-lscale scale

On devices which support line width scaling all line width specifications within the metafile will be scaled by scale. This option is subject to modification by the -lmin and -lmax options.

-movie time

Set pause to time seconds. In normal operation mode the translator requires user interaction after the display of each plot. ctrans will not proceed until the user responds.  If movie mode is set ctrans will wait time seconds after the display of each frame and then proceed automatically. This option and the -pause option are mutually exclusive.

This option may not behave as expected on slower devices.

-outfile file

Direct translator output to file. By default translator output is written to the standard output. This option has no effect for devices of which ctrans has a function-callable interface. e.g. X11 .

-pal pal_fname

Use the color palette defined in the file pal_fname for subsequent translation of the metafile. This palette will override any  color map defined by the CGM being translated. For a description of  the format of pal_fname see ras_palette(5NCARG).


Pause after each frame in the metafile is displayed and wait for the user to type a newline before proceding. This option is probably only useful when used in conjunction with the -wid option as this is the normal behaviour for ctrans in most instances. This option and the -movie option are mutually exclusive.


Suppress reporting of non-fatal (warning) error  messages; only fatal error messages are reported.


< record_number...   >
If processing only single frames of the metafile is desired, this option specifies the record number containing the start of that frame. ctrans assumes the processing is to start at the first BEGIN PICTURE element in that record.  The user must perform bookkeeping to determine the record that contains the desired frame.  Normally, a metafile editor (e.g., ictrans(1NCARG). may be used as the actual user interface to perform this bookkeeping. Without a specified record number, ctrans processes the entire metafile.


Unconditionally perform software filling of all filled polygons. This option may be useful for devices which do not support the filled  polygon drawing  primitive or have limits on the number of vertices describing a polygon. On some devices this number is known and software filling is performed, as appropriate, without user specification.


Operate in verbose mode.


Print the version number and then exit.

-viewport llx:lly:urx:ury

Set the viewport of the output device. The viewport is the rectangular region of the output device of which the virtual device coordinate system of the metafile is mapped onto. Normally this region is the largest device-addressable square which fits in the center of the device address space. The -viewport option may be used to change the default mapping. llx and lly specify the lower left corner of the device in normalized coordinates. urx and ury specify the upper right corner of the device in normalized coordinates. For example, -viewport 0.0 0.0 0.5 0.5, specifies the lower left  corner of the device.

-window llx:lly:urx:ury

Specify the workstation window (in the GKS sense). Four coordinates are specified which define a rectangular window which is a subset of the normalized VDC rectangle with corner points (0,0) and (1.0,1.0). llx and lly specify the lower left corner. urx and .ury specify the upper right corner. The specified window is mapped onto the entire display viewport. For example,  if the workstation window is defined by the corner points (0,0) and (0.5 0.5) then the lower left quarter of a plot would be blown up to fill the entire viewport. Specification of such a window can be used for zooming and panning.

The range with which one may zoom in on a plot may be limited by the integer addressing precision of the device.

Device-Specific Options

The following options are available when the device is graphcap-driven (See the gcaps(1NCARG) command for a list of graphcap-driven devices):


Simulate CGM background color requests by drawing a large filled rectangle  of the appropriate color. This option is useful for devices such as color PostScript printers which have no concept of background color.

The following options are available when device is CTXT:


Suppress display of CGM output primitive data. All other CGM element data is displayed. This may substantially reduce the verbosity of  the clear text driver.


Suppress display of CGM element data except for output primitives. The -Data combined with the -Para option permit the  display of only the CGM element names.

The following options are available when device is X11:

-background color

Specifies the default window background color for color devices. If the  metafile explicitly sets color index 0 then this option is overridden.

-foreground color

Specifies the default foreground color for color devices. If the metafile  explicitly sets color index 1 then this option is overridden.

-geometry geometry

Specify the size and/or position of the graphics window in the format of an X11 Window System geometry string.


Ignore requests to change the background color. This option may be useful when ctrans renders into a X window created by an application other than ctrans. As a side effect of this option the rendering window  is not cleared between frames.


On monochrome devices reverse video is simulated by swapping the foreground and background colors.

-wid window_id

Render into the previously created X window specified by window_id. Normally ctrans creates its own window for plotting. The window specified by window_id must be of type InputOutput. The window must also have inherited its color map, depth and visual class from the root window.

Note also that when this option is used ctrans cannot receive X events from the drawing window. Hence, ctrans cannot use "mouse clicks" as a signal to advance frames. For this reason the -pause option is useful to prevent ctrans from processing the entire metafile without pausing between frames.

window_id may be specified as a decimal or hexidecimal integer.

The following options apply to the X11 color map management of ctrans when device is X11:

ctrans supports three different methods of X11 color map management.

If the user specifies a shared color map (using the -scmap option), then ctrans will use the default X color map for the screen, that is shared by all applications.  If the metafile contains more colors than there are available in the default X color map, then a color matching algorithm is employed.  The idea of the algorithm is that the color in the current color table that is closest to the requested color will be selected. Closest is defined in terms of the normal distance metric on the RGB cube.  If the closest color is equal to or farther away than the percentage error allowed ( -colerr ), then a warning message will be printed.  The closest color is still used.

If the user specifies a private color map (using the -pcmap option), then ctrans will create a private color map for the graphics window.  This will guarantee that 256 distinct colors are available to the window.  This means that the  X window will have a different color map than all the other windows on the screen. Therefore, you usually have to have the mouse pointer in the window for the correct color table to be installed.  One disadvantage to this option is that there is usually a color flashing effect on the screen since the wrong color table will be installed for the other windows on the screen.

The default color map management scheme attempts to take the best of the two previous models.  It starts out behaving like the shared model, in that it uses the default color map for the screen.  It differs in that, once it can't allocate any more colors from the default color map, in allocates its own private color table and starts using it.  This way, the color flashing is only present if it absolutely needs to be so that ctrans can display the correct color.


Ask ctrans to use the shared default X color map only.

This is the option used if -wid is specified.

-colerr n

Specifies the percentage color error that is acceptable if the -scmap option is being used.  If the color being used is n percentage or more different from the color requested, a warning will be reported by ctrans.


Ask ctrans to create its own X color map and use it exclusively.

This option is ignored if the -wid option is present.

The following options are available when device is a60, avs, hdf, hppcl, nrif, sun, or xwd:

-dpi dpi

Specify the number of dots per inch. This option is only meaningful for the HP LaserJet, hppcl, which ignores the -resolution option. dpi may be one of 75, 100, 150, or 300. The default is 150.


By default ctrans outputs raster imagery with 8-bit-indexed encoding. When this option is used, if the raster file format supports it, raster imagery is output in a 24-bit-direct encoding scheme. Be warned: the resultant file is three times the size of its 8-bit-indexed counterpart.


Generate the image in landscape mode. This option is ignored by all  raster devices except the HP LaserJet, hppcl. By default the LaserJet uses portrait mode.

-resolution widthxheight

width and height specify the spatial resolution in pixels of the raster file to be created. The default is 512x512.


To process a metafile named gmeta and display its contents on the TEKTRONIX 4107 terminal, use the following call:

% ctrans -d t4107 gmeta

If this device is already defined by the GRAPHCAP environment variable, simply call:

% ctrans gmeta

If you wish to display only the first  frame starting in the third record, call:

% ctrans -record 3 -d t4107 gmeta

To examine the metafile gmeta's contents without CGM element data being displayed:

% ctrans -d CTXT -Data -Para gmeta

To render the metafile gmeta (under X Windows) in a window that is 512x512 pixels in dimension in the lower right corner of your screen

% ctrans -d X11 -geometry 512x512-0-0 gmeta

To rasterize the contents of the metafile   gmeta at a resolution of 1024x1024 pixels, call:

% ctrans -d xwd -res 1024x1024 > raster.xwd

The raster output is in X11 "xwd" format and is sent to the file raster.xwd.

To zoom in on the upper right quarter of the metafile gmeta and display it in an X window, call:

% ctrans -d X11 -window 0.5:0.5:1.0:1.0



Default fontcap specifier.


Default output device specifier.


Path to root of NCAR Graphics installation.


If set this variable contains the path to the installed NCAR Graphics  libraries. NCARG_LIB overrides NCARG_ROOT.


If set, this environment variable contains a directory path to be used for temporary files. On most systems the default is /tmp. On some systems the default is /usr/tmp.



The binary NCAR Graphcap files


The binary NCAR Fontcap files

See Also

fcaps(1NCARG), fontcap(5NCARG), gcaps(1NCARG), graphcap(5NCARG), idt(1NCARG), ras_palette(5NCARG), med(1NCARG), ictrans(1NCARG)

Hardcopy: NCAR Graphics Fundamentals, UNIX Version


Running in "movie" mode may give surprising results on slower devices,  such as dumb terminals. If too short a time interval is specified slow devices may not have finished rendering before the movie timer expires. This results in no pause between frames.  

Metafiles which reference color table indices that were not previously  defined may have varying results from one device to the next.

Using the -wid option to have ctrans display its output in a window created by another X application may produce unexpected results, particularly with regard to color.

At ctrans' current level of implementation, the subset of CGM elements  supported is closely approximated by the list provided in NCAR's Graphics Installer's Guide, Version 2.00 (August 1987). However, the best way to determine whether a particular CGM element is supported by the translator is feed a metafile containing the element in question to ctrans. Consult the aforementioned publication for a discussion of  Graphcaps and Fontcaps as well.