Figure.logo: Add Pythonic parameters to specify the location and size

examples/gallery/embellishments/gmt_logo.py

@@ -13,6 +13,5 @@
 
 # Add the GMT logo in the Top Right (TR) corner of the current plot, scaled up to be 3
 # centimeters wide and offset by 0.3 cm in x-direction and 0.6 cm in y-direction.
-fig.logo(position="jTR+o0.3c/0.6c+w3c")
-
+fig.logo(position="TR", position_type="inside", anchor_offset=(0.3, 0.6), width="3c")
 fig.show()

pygmt/src/inset.py

@@ -140,9 +140,8 @@ def inset(
     ...         dcw="MG+gred",
     ...     )
     ...
-    >>> # Map elements outside the "with" statement are plotted in the main
-    >>> # figure
-    >>> fig.logo(position="jBR+o0.2c+w3c")
+    >>> # Map elements outside the "with" statement are plotted in the main figure
+    >>> fig.logo(position="BR", position_type="inside", offset=0.2, width="3c")
     >>> fig.show()
     """
     self._activate_figure()

pygmt/src/logo.py

@@ -2,23 +2,29 @@
 logo - Plot the GMT logo.
 """
 
+from collections.abc import Sequence
 from typing import Literal
 
-from pygmt.alias import AliasSystem
+from pygmt._typing import AnchorCode
+from pygmt.alias import Alias, AliasSystem
 from pygmt.clib import Session
+from pygmt.exceptions import GMTInvalidInput
 from pygmt.helpers import build_arg_list, fmt_docstring, kwargs_to_strings, use_alias
 
 
 @fmt_docstring
-@use_alias(
-    R="region",
-    D="position",
-    F="box",
-    S="style",
-)
+@use_alias(R="region", F="box", S="style")
 @kwargs_to_strings(R="sequence", p="sequence")
-def logo(
+def logo(  # noqa: PLR0913
     self,
+    position: Sequence[str | float] | AnchorCode | None = None,
+    position_type: Literal[
+        "mapcoords", "boxcoords", "plotcoords", "inside", "outside"
+    ] = "plotcoords",
+    anchor: AnchorCode | None = None,
+    anchor_offset: Sequence[float | str] | None = None,
+    height: float | str | None = None,
+    width: float | str | None = None,
     projection=None,
     verbose: Literal["quiet", "error", "warning", "timing", "info", "compat", "debug"]
     | bool = False,
@@ -29,27 +35,66 @@ def logo(
     r"""
     Plot the GMT logo.
 
-    By default, the GMT logo is 2 inches wide and 1 inch high and
-    will be positioned relative to the current plot origin.
-    Use various options to change this and to place a transparent or
-    opaque rectangular map panel behind the GMT logo.
+    .. figure:: https://docs.generic-mapping-tools.org/6.5/_images/GMT_coverlogo.png
+       :alt: GMT logo
+       :align: center
+       :width: 300px
+
+    By default, the GMT logo is 2 inches wide and 1 inch high and will be positioned
+    relative to the current plot origin. The position can be changed by specifying the
+    reference point (via ``position_type`` and ``position``) and anchor point (via
+    ``anchor`` and ``anchor_offset``). Refer to :doc:`/techref/reference_anchor_points`
+    for details about the positioning.
 
     Full GMT docs at :gmt-docs:`gmtlogo.html`.
 
     {aliases}
+       - D = position/position_type/anchor/anchor_offset/width/height
        - J = projection
        - V = verbose
        - c = panel
        - t = transparency
 
     Parameters
     ----------
-    {projection}
-    {region}
-    position : str
-        [**g**\|\ **j**\|\ **J**\|\ **n**\|\ **x**]\ *refpoint*\
-        **+w**\ *width*\ [**+j**\ *justify*]\ [**+o**\ *dx*\ [/*dy*]].
-        Set reference point on the map for the image.
+    position/position_type
+        Specify the reference point on the plot for the GMT logo. The method of
+        defining the the reference point is controlled by **position_type**, and the
+        exact location is set by **position**.
+
+        The **position_type** parameter can take one of the following values:
+
+        - ``"mapcoords"``: **position** is specified as (*longitude*, *latitude*) in map
+          coordinates. Example: (120, -45) places the reference point at 120°E, 45°S.
+        - ``"boxcoords"``: **position** is specified as (*nx*, *ny*) in normalized
+          coordinates, i.e., fractional values between 0 and 1 along the x- and y-axes.
+          Example: (0, 0) corresponds to the lower-left corner, and (1, 1) to the
+          upper-right corner of the plot bounding box.
+        - ``"plotcoords"``: **position** is specified as (*x*, *y*) in plot coordinates,
+          i.e., distances from the lower-left plot origin given in inches, centimeters,
+          or points. Example: ("1c", "2c") places the reference point 1 cm to the right
+          and 2 cm above the plot origin.
+        - ``"inside"`` or ``"outside"``: **position** is one of the nine
+          :doc:two-character justification codes </techref/justification_codes>,
+          indicating a specific location relative to the plot bounding box. Example:
+          ``"TL"`` places the reference point at the top-left corner, either inside or
+          outside the bounding box.
+    anchor
+        Specify the anchor point of the GMT logo, using one of the
+        :doc:`2-character justification codes </techref/justification_codes>`.
+        The default value depends on **position_type**.
+
+        - ``position_type="inside"``: **anchor** defaults to the same as **position**.
+        - ``position_type="outside"``: **anchor** defaults to the mirror opposite of
+          **position**.
+        - Otherwise, **anchor** defaults to ``"MC"`` (middle center).
+    anchor_offset
+        Specifies an offset for the anchor point as *offset* or
+        (*offset_x*, *offset_y*). If a single value *offset* is given, both *offset_x*
+        and *offset_y* are set to *offset*.
+    width/height
+        Width or height of the GMT logo. Since the aspect ratio is fixed, only one of
+        the two can be specified.
     box : bool or str
         If set to ``True``, draw a rectangular border around the
         GMT logo.
@@ -61,13 +106,51 @@ def logo(
           [Default]
         - **n** to skip the label placement
         - **u** to place the URL to the GMT site
+    {projection}
+    {region}
     {verbose}
     {panel}
     {transparency}
     """
     self._activate_figure()
 
-    aliasdict = AliasSystem().add_common(
+    # width and height are mutually exclusive.
+    if width is not None and height is not None:
+        msg = "Cannot specify both width and height."
+        raise GMTInvalidInput(msg)
+
+    # Mapping position_type to GMT single-letter code.
+    _position_type = {
+        "mapcoords": "g",
+        "boxcoords": "n",
+        "plotcoords": "x",
+        "inside": "j",
+        "outside": "J",
+    }[position_type]
+
+    # Prior PyGMT v0.17.0, 'position' was aliased to the -D option.
+    # For backward compatibility, we need to check if users pass a string with the GMT
+    # CLI syntax to 'position', i.e., a string starting with one of the leading
+    # single-letter or contains modifiers with "+".
+    if isinstance(position, str) and (position[0] in "gnxjJ" or "+" in position):
+        if any(v is not None for v in (anchor, anchor_offset, height, width)):
+            msg = (
+                "Parameter 'position' is given with a raw GMT CLI syntax, and conflicts "
+                "with other parameters (anchor, anchor_offset, height, width). "
+                "Please refer to the documentation for the recommended usage."
+            )
+            raise GMTInvalidInput(msg)
+        _position_type = ""  # Unset _position_type to an empty string.
+
+    aliasdict = AliasSystem(
+        D=[
+            Alias(position, name="position", sep="/", size=2, prefix=_position_type),
+            Alias(anchor, name="anchor", prefix="+j"),
+            Alias(anchor_offset, name="anchor_offset", prefix="+o", sep="/", size=2),
+            Alias(height, name="height", prefix="+h"),
+            Alias(width, name="width", prefix="+w"),
+        ]
+    ).add_common(
         J=projection,
         V=verbose,
         c=panel,

pygmt/tests/test_logo.py

@@ -4,6 +4,7 @@
 
 import pytest
 from pygmt import Figure
+from pygmt.exceptions import GMTInvalidInput
 
 
 @pytest.mark.benchmark
@@ -24,5 +25,48 @@ def test_logo_on_a_map():
     """
     fig = Figure()
     fig.basemap(region=[-90, -70, 0, 20], projection="M15c", frame=True)
-    fig.logo(position="jTR+o0.25c/0.25c+w7.5c", box=True)
+    fig.logo(
+        position_type="inside",
+        position="TR",
+        anchor_offset=(0.25, 0.25),
+        width="7.5c",
+        box=True,
+    )
     return fig
+
+
+@pytest.mark.mpl_image_compare(filename="test_logo_position_deprecated_syntax.png")
+def test_logo_position():
+    """
+    Test that the new group of parameters works as expected.
+    """
+    fig = Figure()
+    fig.basemap(region=[-90, -70, 0, 20], projection="M15c", frame=True)
+    fig.logo(position="TL", position_type="inside")
+    fig.logo(position="TR", position_type="inside", width="7.5c")
+    fig.logo(position=(6, 0), width="7.5c")
+    fig.logo(position=(0, 0))
+    return fig
+
+
+@pytest.mark.mpl_image_compare
+def test_logo_position_deprecated_syntax():
+    """
+    Test that passing the deprecated GMT CLI syntax string to 'position' works.
+    """
+    fig = Figure()
+    fig.basemap(region=[-90, -70, 0, 20], projection="M15c", frame=True)
+    fig.logo(position="jTL")
+    fig.logo(position="jTR+w7.5c")
+    fig.logo(position="6/0+w7.5c")
+    fig.logo(position="0/0")  # This is actually the new syntax.
+    return fig
+
+
+def test_logo_width_and_height():
+    """
+    Test that an error is raised when both width and height are specified.
+    """
+    fig = Figure()
+    with pytest.raises(GMTInvalidInput):
+        fig.logo(width="5c", height="5c")