add support for arcs

README.rst

@@ -63,6 +63,7 @@ Usage Example
     import displayio
     from adafruit_display_shapes.rect import Rect
     from adafruit_display_shapes.circle import Circle
+    from adafruit_display_shapes.arc import Arc
     from adafruit_display_shapes.roundrect import RoundRect
 
     splash = displayio.Group()
@@ -84,6 +85,9 @@ Usage Example
     circle = Circle(100, 100, 20, fill=0x00FF00, outline=0xFF00FF)
     splash.append(circle)
 
+    arc = Arc(x=100, y=100, radius=25, angle=45, direction=90, segments=10, outline=0x00FF00)
+    splash.append(arc)
+
     rect2 = Rect(50, 100, 61, 81, outline=0x0, stroke=3)
     splash.append(rect2)
 

adafruit_display_shapes/arc.py

@@ -0,0 +1,107 @@
+# SPDX-FileCopyrightText: 2023 Bernhard Bablok
+#
+# SPDX-License-Identifier: MIT
+
+"""
+`arc`
+================================================================================
+
+Various common shapes for use with displayio - Arc shape!
+
+
+* Author(s): Bernhard Bablok
+
+Implementation Notes
+--------------------
+
+**Software and Dependencies:**
+
+* Adafruit CircuitPython firmware for the supported boards:
+  https://github.com/adafruit/circuitpython/releases
+
+"""
+
+try:
+    from typing import Optional
+except ImportError:
+    pass
+
+import math
+import displayio
+from adafruit_display_shapes.polygon import Polygon
+
+try:
+    import vectorio
+
+    HAVE_VECTORIO = True
+except ImportError:
+    HAVE_VECTORIO = False
+
+__version__ = "0.0.0+auto.0"
+__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_Display_Shapes.git"
+
+
+class Arc(displayio.Group):
+    # pylint: disable=too-few-public-methods, invalid-name
+    """An arc. Technically, an arc is a Group with one or two polygons.
+
+    An arc is defined by a radius, an angle (in degrees) and a direction (also in
+    degrees). The latter is the direction of the midpoint of the arc.
+
+    The direction-parameter uses the layout of polar-coordinates, i.e. zero points
+    to the right, 90 to the top, 180 to the left and 270 to the bottom.
+
+    The Arc-class creates the arc as a polygon. The number of segments define
+    how round the arc is. There is a memory-tradeoff if the segment-number is
+    large.
+
+    :param float radius: The (outer) radius of the arc.
+    :param float angle: The angle of the arc in degrees.
+    :param float direction: The direction of the middle-point of the arc in degrees (0)
+    :param int segments: The number of segments of the arc.
+    :param arc_width int: (Optional) The width of the arc. This creates an inner arc as well.
+    :param int|None outline: The outline of the arc. Can be a hex value for a color or
+                    ``None`` for no outline.
+    :param int|None fill: The fill-color of the arc. Can be a hex value for a color or
+                    ``None`` for no filling. Ignored if port does not support vectorio.
+    """
+
+    def __init__(
+        # pylint: disable=too-many-arguments, too-many-locals
+        self,
+        radius: float,
+        angle: float,
+        direction: float,
+        segments: int,
+        *args,
+        arc_width: Optional[int] = 1,
+        outline: Optional[int] = None,
+        fill: Optional[int] = None,
+        **kwargs,
+    ) -> None:
+        super().__init__(*args, **kwargs)
+        # shift direction by angle/2
+        direction = direction - angle / 2
+        # create outer points
+        points = []
+        for i in range(segments + 1):
+            alpha = (i * angle / segments + direction) / 180 * math.pi
+            x0 = int(radius * math.cos(alpha))
+            y0 = -int(radius * math.sin(alpha))
+            points.append((x0, y0))
+
+        # create inner points
+        if arc_width > 1:
+            for i in range(segments, -1, -1):
+                alpha = (i * angle / segments + direction) / 180 * math.pi
+                x0 = int((radius - arc_width) * math.cos(alpha))
+                y0 = -int((radius - arc_width) * math.sin(alpha))
+                points.append((x0, y0))
+
+        # create polygon(s) and add to ourselves
+        if arc_width > 1 and HAVE_VECTORIO and fill is not None:
+            palette = displayio.Palette(1)
+            palette[0] = fill
+            self.append(vectorio.Polygon(pixel_shader=palette, points=points, x=0, y=0))
+        if outline is not None:
+            self.append(Polygon(points, outline=outline, colors=1, close=arc_width > 1))

docs/api.rst

@@ -24,3 +24,6 @@
 
 .. automodule:: adafruit_display_shapes.sparkline
   :members:
+
+.. automodule:: adafruit_display_shapes.arc
+  :members:

docs/examples.rst

@@ -51,3 +51,12 @@ Example showing the features of the new Circle setter
 .. literalinclude:: ../examples/display_shapes_circle_animation.py
     :caption: examples/display_shapes_circle_animation.py
     :linenos:
+
+Arc Simple Test
+---------------
+
+Example demonstrating various arcs.
+
+.. literalinclude:: ../examples/display_shapes_arc.py
+    :caption: examples/display_shapes_arc.py
+    :linenos:

examples/display_shapes_arc.py

@@ -0,0 +1,73 @@
+# SPDX-FileCopyrightText: 2023 Bernhard Bablok
+# SPDX-License-Identifier: MIT
+
+import time
+import board
+
+import displayio
+from adafruit_display_shapes.arc import Arc
+from adafruit_display_shapes.circle import Circle
+
+# use built in display (PyPortal, PyGamer, PyBadge, CLUE, etc.)
+# see guide for setting up external displays (TFT / OLED breakouts, RGB matrices, etc.)
+# https://learn.adafruit.com/circuitpython-display-support-using-displayio/display-and-display-bus
+display = board.DISPLAY
+
+w2 = int(display.width / 2)
+h2 = int(display.height / 2)
+
+WHITE = 0xFFFFFF
+RED = 0xFF0000
+GREEN = 0x00FF00
+BLUE = 0x0000FF
+
+# Make the display context
+group = displayio.Group()
+display.root_group = group
+
+# little circle in the center of all arcs
+circle = Circle(w2, h2, 5, fill=0xFF0000, outline=0xFF0000)
+group.append(circle)
+
+# red arc with white outline, 10 pixels wide
+arc1 = Arc(
+    x=w2,
+    y=h2,
+    radius=min(display.width, display.height) / 4,
+    angle=90,
+    direction=90,
+    segments=10,
+    arc_width=10,
+    outline=WHITE,
+    fill=RED,
+)
+group.append(arc1)
+
+# green arc (single line)
+arc2 = Arc(
+    x=w2,
+    y=h2,
+    radius=min(display.width, display.height) / 4 + 5,
+    angle=180,
+    direction=90,
+    segments=20,
+    arc_width=1,
+    outline=GREEN,
+)
+group.append(arc2)
+
+# blue arc (or pie)
+arc3 = Arc(
+    x=w2,
+    y=h2,
+    radius=min(display.width, display.height) / 4,
+    angle=90,
+    direction=-90,
+    segments=10,
+    arc_width=min(display.width, display.height) / 4 - 5,
+    outline=BLUE,
+)
+group.append(arc3)
+
+while True:
+    time.sleep(0.1)