Add the Pattern class

Author: seisman

pygmt/params/__init__.py

@@ -3,3 +3,4 @@
 """
 
 from pygmt.params.box import Box
+from pygmt.params.pattern import Pattern

pygmt/params/pattern.py

@@ -0,0 +1,65 @@
+"""
+The Pattern class for specifying GMT filling patterns.
+"""
+
+import dataclasses
+
+from pygmt.alias import Alias
+from pygmt.params.base import BaseParam
+from pygmt.exceptions import GMTValueError
+
+
+@dataclasses.dataclass(repr=False)
+class Pattern(BaseParam):
+    """
+
+    Examples
+    --------
+    >>> from pygmt.params import Pattern
+    >>> str(Pattern(id=1))
+    'p1'
+    >>> str(Pattern(id=1, bgcolor="red", fgcolor="blue"))
+    'p1+bred+fblue'
+    >>> str(Pattern(id=1, bgcolor="red", fgcolor="blue", dpi=300))
+    'p1+bred+fblue+r300'
+    >>> str(Pattern(id="my_pattern.png"))
+    'pmy_pattern.png'
+    >>> str(Pattern(id=2, reversed=True))
+    'P2'
+    >>> str(Pattern(id=100))
+    Traceback (most recent call last):
+        ...
+    pygmt.exceptions.GMTValueError: Invalid pattern id: 100...
+    """
+
+    id: int | str
+    reversed: bool = False
+    bgcolor: str | None = None
+    fgcolor: str | None = None
+    dpi: int | None = None
+
+    def __post_init__(self):
+        """
+        Validate the id and set the reversed flag.
+        """
+        if isinstance(self.id, int) and not (1 <= self.id <= 90):
+            raise GMTValueError(
+                self.id,
+                description="pattern id",
+                reason=(
+                    "Pattern id must be an integer in the range 1-90 "
+                    "or the name of a 1-, 8-, or 24-bit image raster file"
+                ),
+            )
+
+    @property
+    def _aliases(self):
+        """
+        Aliases for the Pattern class.
+        """
+        return [
+            Alias(self.id, name="id", prefix="P" if self.reversed else "p"),
+            Alias(self.bgcolor, name="bgcolor", prefix="+b"),
+            Alias(self.fgcolor, name="fgcolor", prefix="+f"),
+            Alias(self.dpi, name="dpi", prefix="+r"),
+        ]