Added ImageDraw rounded_rectangle method

Tests/test_imagedraw.py

@@ -706,6 +706,58 @@ def test_rectangle_translucent_outline():
     )
 
 
+@pytest.mark.parametrize(
+    "xy",
+    [(10, 20, 190, 180), ([10, 20], [190, 180]), ((10, 20), (190, 180))],
+)
+def test_rounded_rectangle(xy):
+    # Arrange
+    im = Image.new("RGB", (200, 200))
+    draw = ImageDraw.Draw(im)
+
+    # Act
+    draw.rounded_rectangle(xy, 30, fill="red", outline="green", width=5)
+
+    # Assert
+    assert_image_equal_tofile(im, "Tests/images/imagedraw_rounded_rectangle.png")
+
+
+def test_rounded_rectangle_zero_radius():
+    # Arrange
+    im = Image.new("RGB", (W, H))
+    draw = ImageDraw.Draw(im)
+
+    # Act
+    draw.rounded_rectangle(BBOX1, 0, fill="blue", outline="green", width=5)
+
+    # Assert
+    assert_image_equal_tofile(im, "Tests/images/imagedraw_rectangle_width_fill.png")
+
+
+@pytest.mark.parametrize(
+    "xy, suffix",
+    [
+        ((20, 10, 80, 90), "x"),
+        ((10, 20, 90, 80), "y"),
+        ((20, 20, 80, 80), "both"),
+    ],
+)
+def test_rounded_rectangle_translucent(xy, suffix):
+    # Arrange
+    im = Image.new("RGB", (W, H))
+    draw = ImageDraw.Draw(im, "RGBA")
+
+    # Act
+    draw.rounded_rectangle(
+        xy, 30, fill=(255, 0, 0, 127), outline=(0, 255, 0, 127), width=5
+    )
+
+    # Assert
+    assert_image_equal_tofile(
+        im, "Tests/images/imagedraw_rounded_rectangle_" + suffix + ".png"
+    )
+
+
 def test_floodfill():
     red = ImageColor.getrgb("red")
 

docs/reference/ImageDraw.rst

@@ -285,6 +285,20 @@ Methods
 
         .. versionadded:: 5.3.0
 
+.. py:method:: ImageDraw.rounded_rectangle(xy, radius=0, fill=None, outline=None, width=1)
+
+    Draws a rounded rectangle.
+
+    :param xy: Two points to define the bounding box. Sequence of either
+            ``[(x0, y0), (x1, y1)]`` or ``[x0, y0, x1, y1]``. The second point
+            is just outside the drawn rectangle.
+    :param radius: Radius of the corners.
+    :param outline: Color to use for the outline.
+    :param fill: Color to use for the fill.
+    :param width: The line width, in pixels.
+
+    .. versionadded:: 8.2.0
+
 .. py:method:: ImageDraw.shape(shape, fill=None, outline=None)
 
     .. warning:: This method is experimental.

docs/releasenotes/8.2.0.rst

@@ -13,10 +13,20 @@ when Tk/Tcl 8.5 will be the minimum supported.
 API Changes
 ===========
 
-TODO
-^^^^
+ImageDraw.rounded_rectangle
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-TODO
+Added :py:meth:`~PIL.ImageDraw.ImageDraw.rounded_rectangle`. It works the same as
+:py:meth:`~PIL.ImageDraw.ImageDraw.rectangle`, except with an additional ``radius``
+argument. ``radius`` is limited to half of the width or the height, so that users can
+create a circle, but not any other ellipse.
+
+.. code-block:: python
+
+    from PIL import Image, ImageDraw
+    im = Image.new("RGB", (200, 200))
+    draw = ImageDraw.Draw(im)
+    draw.rounded_rectangle(xy=(10, 20, 190, 180), radius=30, fill="red")
 
 API Additions
 =============

src/PIL/ImageDraw.py

@@ -257,6 +257,96 @@ def rectangle(self, xy, fill=None, outline=None, width=1):
         if ink is not None and ink != fill and width != 0:
             self.draw.draw_rectangle(xy, ink, 0, width)
 
+    def rounded_rectangle(self, xy, radius=0, fill=None, outline=None, width=1):
+        """Draw a rounded rectangle."""
+        if isinstance(xy[0], (list, tuple)):
+            (x0, y0), (x1, y1) = xy
+        else:
+            x0, y0, x1, y1 = xy
+
+        d = radius * 2
+
+        full_x = d >= x1 - x0
+        if full_x:
+            # The two left and two right corners are joined
+            d = x1 - x0
+        full_y = d >= y1 - y0
+        if full_y:
+            # The two top and two bottom corners are joined
+            d = y1 - y0
+        if full_x and full_y:
+            # If all corners are joined, that is a circle
+            return self.ellipse(xy, fill, outline, width)
+
+        if d == 0:
+            # If the corners have no curve, that is a rectangle
+            return self.rectangle(xy, fill, outline, width)
+
+        ink, fill = self._getink(outline, fill)
+
+        def draw_corners(pieslice):
+            if full_x:
+                # Draw top and bottom halves
+                parts = (
+                    ((x0, y0, x0 + d, y0 + d), 180, 360),
+                    ((x0, y1 - d, x0 + d, y1), 0, 180),
+                )
+            elif full_y:
+                # Draw left and right halves
+                parts = (
+                    ((x0, y0, x0 + d, y0 + d), 90, 270),
+                    ((x1 - d, y0, x1, y0 + d), 270, 90),
+                )
+            else:
+                # Draw four separate corners
+                parts = (
+                    ((x1 - d, y0, x1, y0 + d), 270, 360),
+                    ((x1 - d, y1 - d, x1, y1), 0, 90),
+                    ((x0, y1 - d, x0 + d, y1), 90, 180),
+                    ((x0, y0, x0 + d, y0 + d), 180, 270),
+                )
+            for part in parts:
+                if pieslice:
+                    self.draw.draw_pieslice(*(part + (fill, 1)))
+                else:
+                    self.draw.draw_arc(*(part + (ink, width)))
+
+        if fill is not None:
+            draw_corners(True)
+
+            if full_x:
+                self.draw.draw_rectangle(
+                    (x0, y0 + d / 2 + 1, x1, y1 - d / 2 - 1), fill, 1
+                )
+            else:
+                self.draw.draw_rectangle(
+                    (x0 + d / 2 + 1, y0, x1 - d / 2 - 1, y1), fill, 1
+                )
+            if not full_x and not full_y:
+                self.draw.draw_rectangle(
+                    (x0, y0 + d / 2 + 1, x0 + d / 2, y1 - d / 2 - 1), fill, 1
+                )
+                self.draw.draw_rectangle(
+                    (x1 - d / 2, y0 + d / 2 + 1, x1, y1 - d / 2 - 1), fill, 1
+                )
+        if ink is not None and ink != fill and width != 0:
+            draw_corners(False)
+
+            if not full_x:
+                self.draw.draw_rectangle(
+                    (x0 + d / 2 + 1, y0, x1 - d / 2 - 1, y0 + width - 1), ink, 1
+                )
+                self.draw.draw_rectangle(
+                    (x0 + d / 2 + 1, y1 - width + 1, x1 - d / 2 - 1, y1), ink, 1
+                )
+            if not full_y:
+                self.draw.draw_rectangle(
+                    (x0, y0 + d / 2 + 1, x0 + width - 1, y1 - d / 2 - 1), ink, 1
+                )
+                self.draw.draw_rectangle(
+                    (x1 - width + 1, y0 + d / 2 + 1, x1, y1 - d / 2 - 1), ink, 1
+                )
+
     def _multiline_check(self, text):
         """Draw text."""
         split_character = "\n" if isinstance(text, str) else b"\n"