Merge pull request #4846 from comhar/features/compute_polygon_coordinates

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Hugo van Kemenade 2020-09-04 23:28:43 +03:00 committed by GitHub
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@ -1093,3 +1093,95 @@ def test_same_color_outline():
# Assert
expected = f"Tests/images/imagedraw_outline_{operation}_{mode}.png"
assert_image_similar_tofile(im, expected, 1)
@pytest.mark.parametrize(
"n_sides, rotation, polygon_name",
[(4, 0, "square"), (8, 0, "regular_octagon"), (4, 45, "square")],
)
def test_draw_regular_polygon(n_sides, rotation, polygon_name):
im = Image.new("RGBA", size=(W, H), color=(255, 0, 0, 0))
filename_base = f"Tests/images/imagedraw_{polygon_name}"
filename = (
f"{filename_base}.png"
if rotation == 0
else f"{filename_base}_rotate_{rotation}.png"
)
draw = ImageDraw.Draw(im)
bounding_circle = ((W // 2, H // 2), 25)
draw.regular_polygon(bounding_circle, n_sides, rotation=rotation, fill="red")
assert_image_equal(im, Image.open(filename))
@pytest.mark.parametrize(
"n_sides, expected_vertices",
[
(3, [(28.35, 62.5), (71.65, 62.5), (50.0, 25.0)]),
(4, [(32.32, 67.68), (67.68, 67.68), (67.68, 32.32), (32.32, 32.32)]),
(
5,
[
(35.31, 70.23),
(64.69, 70.23),
(73.78, 42.27),
(50.0, 25.0),
(26.22, 42.27),
],
),
(
6,
[
(37.5, 71.65),
(62.5, 71.65),
(75.0, 50.0),
(62.5, 28.35),
(37.5, 28.35),
(25.0, 50.0),
],
),
],
)
def test_compute_regular_polygon_vertices(n_sides, expected_vertices):
bounding_circle = (W // 2, H // 2, 25)
vertices = ImageDraw._compute_regular_polygon_vertices(bounding_circle, n_sides, 0)
assert vertices == expected_vertices
@pytest.mark.parametrize(
"n_sides, bounding_circle, rotation, expected_error, error_message",
[
(None, (50, 50, 25), 0, TypeError, "n_sides should be an int"),
(1, (50, 50, 25), 0, ValueError, "n_sides should be an int > 2"),
(3, 50, 0, TypeError, "bounding_circle should be a tuple"),
(
3,
(50, 50, 100, 100),
0,
ValueError,
"bounding_circle should contain 2D coordinates "
"and a radius (e.g. (x, y, r) or ((x, y), r) )",
),
(
3,
(50, 50, "25"),
0,
ValueError,
"bounding_circle should only contain numeric data",
),
(
3,
((50, 50, 50), 25),
0,
ValueError,
"bounding_circle centre should contain 2D coordinates (e.g. (x, y))",
),
(3, (50, 50, 0), 0, ValueError, "bounding_circle radius should be > 0",),
(3, (50, 50, 25), "0", ValueError, "rotation should be an int or float",),
],
)
def test_compute_regular_polygon_vertices_input_error_handling(
n_sides, bounding_circle, rotation, expected_error, error_message
):
with pytest.raises(expected_error) as e:
ImageDraw._compute_regular_polygon_vertices(bounding_circle, n_sides, rotation)
assert str(e.value) == error_message

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@ -254,6 +254,24 @@ Methods
:param outline: Color to use for the outline.
:param fill: Color to use for the fill.
.. py:method:: ImageDraw.regular_polygon(bounding_circle, n_sides, rotation=0, fill=None, outline=None)
Draws a regular polygon inscribed in ``bounding_circle``,
with ``n_sides``, and rotation of ``rotation`` degrees.
:param bounding_circle: The bounding circle is a tuple defined
by a point and radius.
(e.g. ``bounding_circle=(x, y, r)`` or ``((x, y), r)``).
The polygon is inscribed in this circle.
:param n_sides: Number of sides
(e.g. ``n_sides=3`` for a triangle, ``6`` for a hexagon).
:param rotation: Apply an arbitrary rotation to the polygon
(e.g. ``rotation=90``, applies a 90 degree rotation).
:param fill: Color to use for the fill.
:param outline: Color to use for the outline.
.. py:method:: ImageDraw.rectangle(xy, fill=None, outline=None, width=1)
Draws a rectangle.

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@ -242,6 +242,13 @@ class ImageDraw:
if ink is not None and ink != fill:
self.draw.draw_polygon(xy, ink, 0)
def regular_polygon(
self, bounding_circle, n_sides, rotation=0, fill=None, outline=None
):
"""Draw a regular polygon."""
xy = _compute_regular_polygon_vertices(bounding_circle, n_sides, rotation)
self.polygon(xy, fill, outline)
def rectangle(self, xy, fill=None, outline=None, width=1):
"""Draw a rectangle."""
ink, fill = self._getink(outline, fill)
@ -555,6 +562,123 @@ def floodfill(image, xy, value, border=None, thresh=0):
edge = new_edge
def _compute_regular_polygon_vertices(bounding_circle, n_sides, rotation):
"""
Generate a list of vertices for a 2D regular polygon.
:param bounding_circle: The bounding circle is a tuple defined
by a point and radius. The polygon is inscribed in this circle.
(e.g. ``bounding_circle=(x, y, r)`` or ``((x, y), r)``)
:param n_sides: Number of sides
(e.g. ``n_sides=3`` for a triangle, ``6`` for a hexagon)
:param rotation: Apply an arbitrary rotation to the polygon
(e.g. ``rotation=90``, applies a 90 degree rotation)
:return: List of regular polygon vertices
(e.g. ``[(25, 50), (50, 50), (50, 25), (25, 25)]``)
How are the vertices computed?
1. Compute the following variables
- theta: Angle between the apothem & the nearest polygon vertex
- side_length: Length of each polygon edge
- centroid: Center of bounding circle (1st, 2nd elements of bounding_circle)
- polygon_radius: Polygon radius (last element of bounding_circle)
- angles: Location of each polygon vertex in polar grid
(e.g. A square with 0 degree rotation => [225.0, 315.0, 45.0, 135.0])
2. For each angle in angles, get the polygon vertex at that angle
The vertex is computed using the equation below.
X= xcos(φ) + ysin(φ)
Y= xsin(φ) + ycos(φ)
Note:
φ = angle in degrees
x = 0
y = polygon_radius
The formula above assumes rotation around the origin.
In our case, we are rotating around the centroid.
To account for this, we use the formula below
X = xcos(φ) + ysin(φ) + centroid_x
Y = xsin(φ) + ycos(φ) + centroid_y
"""
# 1. Error Handling
# 1.1 Check `n_sides` has an appropriate value
if not isinstance(n_sides, int):
raise TypeError("n_sides should be an int")
if n_sides < 3:
raise ValueError("n_sides should be an int > 2")
# 1.2 Check `bounding_circle` has an appropriate value
if not isinstance(bounding_circle, (list, tuple)):
raise TypeError("bounding_circle should be a tuple")
if len(bounding_circle) == 3:
*centroid, polygon_radius = bounding_circle
elif len(bounding_circle) == 2:
centroid, polygon_radius = bounding_circle
else:
raise ValueError(
"bounding_circle should contain 2D coordinates "
"and a radius (e.g. (x, y, r) or ((x, y), r) )"
)
if not all(isinstance(i, (int, float)) for i in (*centroid, polygon_radius)):
raise ValueError("bounding_circle should only contain numeric data")
if not len(centroid) == 2:
raise ValueError(
"bounding_circle centre should contain 2D coordinates (e.g. (x, y))"
)
if polygon_radius <= 0:
raise ValueError("bounding_circle radius should be > 0")
# 1.3 Check `rotation` has an appropriate value
if not isinstance(rotation, (int, float)):
raise ValueError("rotation should be an int or float")
# 2. Define Helper Functions
def _apply_rotation(point, degrees, centroid):
return (
round(
point[0] * math.cos(math.radians(360 - degrees))
- point[1] * math.sin(math.radians(360 - degrees))
+ centroid[0],
2,
),
round(
point[1] * math.cos(math.radians(360 - degrees))
+ point[0] * math.sin(math.radians(360 - degrees))
+ centroid[1],
2,
),
)
def _compute_polygon_vertex(centroid, polygon_radius, angle):
start_point = [polygon_radius, 0]
return _apply_rotation(start_point, angle, centroid)
def _get_angles(n_sides, rotation):
angles = []
degrees = 360 / n_sides
# Start with the bottom left polygon vertex
current_angle = (270 - 0.5 * degrees) + rotation
for _ in range(0, n_sides):
angles.append(current_angle)
current_angle += degrees
if current_angle > 360:
current_angle -= 360
return angles
# 3. Variable Declarations
angles = _get_angles(n_sides, rotation)
# 4. Compute Vertices
return [
_compute_polygon_vertex(centroid, polygon_radius, angle) for angle in angles
]
def _color_diff(color1, color2):
"""
Uses 1-norm distance to calculate difference between two values.