.. index:: ! makecpt
.. include:: module_core_purpose.rst_

*******
makecpt
*******

|makecpt_purpose|

Synopsis
--------

.. include:: common_SYN_OPTs.rst_

**gmt makecpt**
[ |-A|\ *transparency*\ [**+a**] ]
[ |-C|\ *cpt* ]
[ |-D|\ [**i**\|\ **o**] ]
[ |-E|\ [*nlevels*] ]
[ |-F|\ [**R**\|\ **c**\|\ **g**\|\ **h**\|\ **r**\|\ **x**][**+c**\ [*label*]][**+k**\ *keys*]]
[ |-G|\ *zlo*\ /\ *zhi* ]
[ |-H| ]
[ |-I|\ [**c**][**z**] ]
[ |-M| ]
[ |-N| ]
[ |-Q| ]
[ |-S|\ *mode* ]
[ |-T|\ [*min*/*max*/*inc*\ [**+b**\|\ **i**\|\ **l**\|\ **n**]\|\ *file*\|\ *list*] ]
[ |-V|\ [*level*] ]
[ |-W|\ [**w**] ]
[ |-Z| ]
[ |SYN_OPT-bi| ]
[ |SYN_OPT-di| ]
[ |SYN_OPT-h| ]
[ |SYN_OPT-i| ]
[ |SYN_OPT--| ]

|No-spaces|

Description
-----------

**makecpt** is a module that will help you make static color palette tables
(CPTs). In classic mode we write the CPT to standard output, while under
modern mode we simply save the CPT as the current session CPT (but see |-H|).
You define an equidistant set of contour intervals or pass
your own z-table or list, and create a new CPT based on an existing master (dynamic)
CPT. The resulting CPT can be reversed relative to the master
cpt, and can be made continuous or discrete.  For color tables beyond the
current GMT offerings, visit `cpt-city <http://soliton.vm.bytemark.co.uk/pub/cpt-city/>`_.

The CPT includes three additional colors beyond the range of
z-values. These are the background color (B) assigned to values lower
than the lowest *z*-value, the foreground color (F) assigned to values
higher than the highest *z*-value, and the NaN color (N) painted
wherever values are undefined.

If the master CPT includes B, F, and N entries, these will be
copied into the new master file. If not, the parameters
:term:`COLOR_BACKGROUND`, :term:`COLOR_FOREGROUND`,
and :term:`COLOR_NAN` from
the :doc:`gmt.conf` file or the command line will be used. This default
behavior can be overruled using the options |-D|, |-M| or |-N|.

The color model (GRAY, RGB, HSV or CMYK) of the palette created by **makecpt**
will be the same as specified in the header of the master CPT. When
there is no :term:`COLOR_MODEL` entry in the master CPT, the
:term:`COLOR_MODEL` specified in the :doc:`gmt.conf` file or on the command
line will be used.

Required Arguments
------------------

None.

Optional Arguments
------------------

.. _-A:

**-A**\ *transparency*\ [**+a**]
    Sets a constant level of transparency (0-100) for all color slices.
    Append **+a** to also affect the fore-, back-, and nan-colors
    [Default is no transparency, i.e., 0 (opaque)].

.. _-C:

.. include:: create_cpt.rst_

.. _-D:

**-D**\ [**i**\|\ **o**]
    Select the back- and foreground colors to match the colors for
    lowest and highest *z*-values in the output CPT [Default (|-D| or **-Do**)
    uses the colors specified in the master file, or those defined by the
    parameters :term:`COLOR_BACKGROUND`, :term:`COLOR_FOREGROUND`, and
    :term:`COLOR_NAN`]. Append **i** to match the colors for the lowest and
    highest values in the input (instead of the output) CPT.

.. _-E:

**-E**\ [*nlevels*]
    Implies reading data table(s) from given command-line files or standard input.
    We use the last data column to determine the data range; use **-i** to
    select another column, and use **-bi** if your data table is native binary.
    This z-range information is used instead of providing the |-T| option.
    We create a linear color table by dividing the table data z-range into
    *nlevels* equidistant slices.  If *nlevels* is not given it defaults to
    the number of levels in the chosen CPT.

.. _-F:

.. include:: explain_cpt_output.rst_

.. _-G:

**-G**\ *zlo*\ /\ *zhi*
    Truncate the incoming CPT so that the lowest and highest z-levels
    are to *zlo* and *zhi*.  If one of these equal NaN then
    we leave that end of the CPT alone.  The truncation takes place
    before any resampling. See also :ref:`manipulating_CPTs`

.. _-H:

**-H**\
    Modern mode only: Write the CPT to standard output as well [Default saves
    the CPT as the session current CPT]. Required for scripts used to make
    animations via :doc:`movie` and :doc:`batch` where we must pass named CPT files.

.. _-I:

**-I**\ [**c**][**z**]
    Append **c** [Default] to reverse the sense of color progression in the master CPT. Also
    exchanges the foreground and background colors, including those
    specified by the parameters :term:`COLOR_BACKGROUND` and
    :term:`COLOR_FOREGROUND`.
    Append **z** to reverse the sign of z-values in the color table.  Note that
    this change of *z*-direction happens before |-G| and |-T| values are used
    so the latter much be compatible with the changed *z*-range.
    See also :ref:`manipulating_CPTs`

.. _-M:

**-M**
    Overrule background, foreground, and NaN colors specified in the
    master CPT with the values of the parameters
    :term:`COLOR_BACKGROUND`, :term:`COLOR_FOREGROUND`,
    and :term:`COLOR_NAN`
    specified in the :doc:`gmt.conf` file or on the command line. When
    combined with |-D|, only :term:`COLOR_NAN` is considered.

.. _-N:

**-N**
    Do not write out the background, foreground, and NaN-color fields [Default will write them].

.. _-Q:

**-Q**
    For logarithmic interpolation scheme with input given as logarithms.
    Expects input z-values provided via |-T| to be :math:`\log_{10}(z)`, assigns colors, and
    writes out *z*.

.. _-S:

**-S**\ *mode*
    Determine a suitable range for the |-T| option from the input table(s) (or standard input).
    Choose from several types of range determinations:
    **-Sr** will use the data range min/max, **-S**\ *inc*\ [**+d**] will use the data min/max but rounded
    to nearest *inc* (append **+d** to resample to a discrete CPT), **-Sa**\ *scl* will
    make a symmetric range around the average (i.e., mean)
    and ±\ *scl* * *sigma*, **-Sm**\ *scl* will make a symmetric range around the median
    and ±\ *scl* * *L1_scale*, **-Sp**\ *scl* will make symmetric range around mode (i.e., LMS; least median of squares) and
    ±\ *scl* * *LMS_scale*, while **-Sq**\ *low/high* sets the range from *low* quartile
    to *high* quartile (in percentages).  We use the last data column for this calculation;
    use **i** if you need to adjust the column orders.

.. _-T:

**-T**\ [*min*/*max*/*inc*\ [**+b**\|\ **i**\|\ **l**\|\ **n**]\|\ *file*\|\ *list*]
    Defines the range of the new CPT by giving the lowest and
    highest z-value (and optionally an interval).  If |-T| is
    not given, the existing range in the master CPT will be used intact.
    The values produced defines the color slice boundaries. If **+n** is
    used it refers to the number of such boundaries and not the number of slices.
    For details on array creation, see `Generate 1-D Array`_. **Note**: To set
    up categorical CPTs with string keys you can also give a comma-separated
    list of your keys.

.. |Add_-V| replace:: |Add_-V_links|
.. include:: explain_-V.rst_
    :start-after: **Syntax**
    :end-before: **Description**

.. _-W:

**-W**\ [**w**]
    Do not interpolate the input color table but pick the output colors
    starting at the beginning of the color table, until colors for all
    intervals are assigned. This is particularly useful in combination
    with a categorical color table, like "categorical". Alternatively,
    use **-Ww** to produce a wrapped (cyclic) color table that endlessly
    repeats its range.

.. _-Z:

**-Z**
    Force a continuous CPT when building from a list of colors and a list of *z*-values [discrete].

.. |Add_-bi| replace:: [Default is the required number of columns given the chosen settings].
.. include:: explain_-bi.rst_

.. |Add_-di| unicode:: 0x20 .. just an invisible code
.. include:: explain_-di.rst_

.. |Add_-h| unicode:: 0x20 .. just an invisible code
.. include:: explain_-h.rst_

.. include:: explain_-icols.rst_

.. include:: explain_help.rst_

.. include:: explain_transparency.rst_

.. include:: explain_array.rst_

Color Hinges
------------

Some of the GMT master dynamic CPTs are actually two separate CPTs
meeting at a *hinge*.  Usually, colors may change dramatically across
the hinge, which is used to separate two different domains (e.g., land
and ocean across the shoreline, for instance).  CPTs with a hinge will
have their two parts stretched to the required range separately, i.e.,
the bottom part up to the hinge will be stretched independently of the
part from the hinge to the top, according to the prescribed new range.
Hinges are either *hard* or *soft*.  Soft hinges must be *activated* by
appending **+h**\ [*hinge*] to the CPT name.
If the selected range does not include an activated soft or hard hinge then
we only resample colors from the half of the CPT that pertains to the range.
See :ref:`Of Colors and Color Legends` for more information.

Discrete versus Continuous CPT
------------------------------

All CPTs can be stretched, but only continuous CPTs can be sampled
at new nodes (i.e., by given an increment in |-T|).  We impose this
limitation to avoid aliasing the original CPT.

Examples
--------

.. include:: explain_example.rst_

To make a CPT with z-values from -200 to 200, with discrete color
changes every 25, and using a polar blue-white-red colortable:

::

  gmt makecpt -Cpolar -T-200/200/25 > colors.cpt

To make an equidistant CPT from z = -2 to 6 using the
continuous default turbo rainbow of colors::

    gmt makecpt -T-2/6 > colors.cpt

To use the GEBCO look-alike CPT with its default range for bathymetry, run::

    gmt makecpt -Cgebco > my_gebco.cpt

or simply use -Cgebco directly in the application that needs the color table.
To create a 24-level color table suitable for plotting the depths in
the remote data table v3206_06.txt (with *lon, lat, depth*), run

::

  gmt makecpt -Cgebco @v3206_06.txt -E24 > my_depths.cpt

To use the gebco color table but reverse the z-values so it can be used for
positive depth values, try

::

  gmt makecpt -Cgebco -Iz > my_positive_gebco.cpt

To make a custom discrete color table for depth of seismicity, using red color for
hypocenters between 0 and 100 km, green for 100-300 km, and blue for deep (300-1000 km)
earthquakes, use

::

  gmt makecpt -Cred,green,blue -T0,80,300,1000 -N > seis.cpt

To make a continuous CPT from white to blue as z goes from
3 to 10, try

::

  gmt makecpt -Cwhite,blue -T3/10 > cold.cpt

To make a wrapped (cyclic) CPT from the jet table over the interval
0 to 500, i.e., the color will be wrapped every 500 z-units so that
we always get a color regardless of the *z* value, try

::

  gmt makecpt -Cjet -T0/500 -Ww > wrapped.cpt

To build a categorical table with 3 categories and add specific category
names to them, try

::

  gmt makecpt -Ccubhelix -T0/2/1 -F+cClouds,Trees,Water > cat.cpt

To instead add unique category labels A, B, C, ... to a 10-item categorical CPT, try

::

  gmt makecpt -Cjet -T0/10/1 -F+cA

To make a categorical CPT with string keys instead of numerical lookup values, try

::

  gmt makecpt -Ccategorical -Twood,water,gold

.. include:: cpt_notes.rst_

See Also
--------

:doc:`gmt`, :doc:`grd2cpt`

References
----------

Crameri, F., (2018). Scientific colour-maps. Zenodo. http://doi.org/10.5281/zenodo.1243862

Crameri, F. (2018), Geodynamic diagnostics, scientific visualisation and StagLab 3.0,
*Geosci. Model Dev.*, 11, 2541-2562, https://doi.org/10.5194/gmd-11-2541-2018.
