Source code for pygmt.src.grdhisteq

"""
grdhisteq - Compute directional gradients from a grid.
"""

import xarray as xr
from pygmt.clib import Session
from pygmt.helpers import (
    GMTTempFile,
    build_arg_string,
    fmt_docstring,
    kwargs_to_strings,
    use_alias,
)


@fmt_docstring
@use_alias(
    C="divisions",
    G="outgrid",
    R="region",
    N="gaussian",
    Q="quadratic",
    V="verbose",
    n="interpolation",
)
@kwargs_to_strings(R="sequence")
def grdhisteq(grid, **kwargs):
    r"""
    Perform histogram equalization for a grid.

    Full option list at :gmt-docs:`grdhisteq.html`

    {aliases}

    Parameters
    ----------
    grid : str or xarray.DataArray
        The file name of the input grid or the grid loaded as a DataArray.
    outgrid : str or None
        The name of the output netCDF file with extension .nc to store the grid
        in.
    divisions : int or str
        The number of divisions of data range to make [Default is 16].

    {R}
    {V}

    Returns
    -------
    ret: xarray.DataArray or None
        Return type depends on whether the ``outgrid`` parameter is set:

        - :class:`xarray.DataArray` if ``outgrid`` is not set
        - None if ``outgrid`` is set (grid output will be stored in file set by
          ``outgrid``)
    """
    with GMTTempFile(suffix=".nc") as tmpfile:
        with Session() as lib:
            file_context = lib.virtualfile_from_data(check_kind="raster", data=grid)
            with file_context as infile:
                if "G" not in kwargs.keys():  # if outgrid is unset, output to tempfile
                    kwargs.update({"G": tmpfile.name})
                outgrid = kwargs["G"]
                arg_str = " ".join([infile, build_arg_string(kwargs)])
                lib.call_module("grdhisteq", arg_str)

        if outgrid == tmpfile.name:  # if user did not set outgrid, return DataArray
            with xr.open_dataarray(outgrid) as dataarray:
                result = dataarray.load()
                _ = result.gmt  # load GMTDataArray accessor information
        else:
            result = None  # if user sets an outgrid, return None

        return result