def __init__(self,
d: str,
canvas_height: float,
transform_origin=True,
transformation=None):
self.canvas_height = canvas_height
self.transform_origin = transform_origin
self.curves = []
self.initial_point = Vector(0, 0) # type: Vector
self.current_point = Vector(0, 0)
self.last_control = None # type: Vector
point_transformation = Transformation()
if self.transform_origin:
point_transformation.add_translation(0, canvas_height)
point_transformation.add_scale(1, -1)
if transformation is not None:
point_transformation.extend(transformation)
self.point_transformation = point_transformation
try:
self._parse_commands(d)
except Exception as generic_exception:
raise generic_exception
warnings.warn(
f"Terminating path. The following unforeseen exception occurred: {generic_exception}"
)
class Path:
"""The Path class represents a generic svg path."""
command_lengths = {
'M': 2,
'm': 2,
'L': 2,
'l': 2,
'H': 1,
'h': 1,
'V': 1,
'v': 1,
'Z': 0,
'z': 0,
'C': 6,
'c': 6,
'Q': 4,
'q': 4,
'S': 4,
's': 4,
'T': 2,
't': 2,
'A': 7,
'a': 7
}
__slots__ = "curves", "initial_point", "current_point", "last_control", "canvas_height", "draw_move", \
"transform_origin", "transformation"
def __init__(self,
d: str,
canvas_height: float,
transform_origin=True,
transformation=None):
self.canvas_height = canvas_height
self.transform_origin = transform_origin
self.curves = []
self.initial_point = Vector(0, 0) # type: Vector
self.current_point = Vector(0, 0)
self.last_control = None # type: Vector
self.transformation = Transformation()
if self.transform_origin:
self.transformation.add_translation(0, canvas_height)
self.transformation.add_scale(1, -1)
if transformation is not None:
self.transformation.extend(transformation)
try:
self._parse_commands(d)
except Exception as generic_exception:
warnings.warn(
f"Terminating path. The following unforeseen exception occurred: {generic_exception}"
)
def __repr__(self):
return f"Path({self.curves})"
def _parse_commands(self, d: str):
"""Parse svg commands (stored in value of the d key) into geometric curves."""
command_key = '' # A character representing a specific command based on the svg standard
command_arguments = [
] # A list containing the arguments for the current command_key
number_str = '' # A buffer used to store numeric characters before conferring them to a number
# Parse each character in d
i = 0
while i < len(d):
character = d[i]
is_numeric = character.isnumeric() or character in [
'-', '.', 'e'
] # Yes, "-6.2e-4" is a valid float.
is_delimiter = character.isspace() or character in [',']
is_command_key = character in self.command_lengths.keys()
is_final = i == len(d) - 1
# If the current command is complete, however the next command does not specify a new key, assume the next
# command has the same key. This is implemented by inserting the current key before the next command and
# restarting the loop without incrementing i
try:
if command_key and len(
command_arguments
) == self.command_lengths[command_key] and is_numeric:
duplicate = command_key
# If a moveto is followed by multiple pairs of coordinates, the subsequent pairs are treated as
# implicit lineto commands. https://www.w3.org/TR/SVG2/paths.html#PathDataMovetoCommands
if command_key == 'm':
duplicate = 'l'
if command_key == 'M':
duplicate = 'L'
d = d[:i] + duplicate + d[i:]
continue
except KeyError as key_error:
warnings.warn(
f"Unknown command key {command_key}. Skipping curve.")
# If the character is part of a number, keep on composing it
if is_numeric:
number_str += character
# if a negative number follows another number, no delimiter is required.
# implicitly stated decimals like .6 don't require a delimiter. In either case we add a delimiter.
negatives = not is_final and character != 'e' and d[i +
1] == '-'
implicit_decimals = not is_final and d[
i + 1] == '.' and '.' in number_str
if negatives or implicit_decimals:
d = d[:i + 1] + ',' + d[i + 1:]
# If the character is a delimiter or a command key or the last character, complete the number and save it
# as an argument
if is_delimiter or is_command_key or is_final:
if number_str:
# In svg form '-.5' can be written as '-.5'. Python doesn't like that notation.
if number_str[0] == '.':
number_str = '0' + number_str
if number_str[0] == '-' and number_str[1] == '.':
number_str = '-0' + number_str[1:]
command_arguments.append(float(number_str))
number_str = ''
# If it's a command key or the last character, parse the previous (now complete) command and save the letter
# as the new command key
if is_command_key or is_final:
if command_key:
self._add_svg_curve(command_key, command_arguments)
command_key = character
command_arguments.clear()
# If the last character is a command key (only useful for Z), save
if is_command_key and is_final:
self._add_svg_curve(command_key, command_arguments)
i += 1
def _add_svg_curve(self, command_key: str, command_arguments: List[float]):
"""
Offer a representation of a curve using the geometry sub-module.
Based on Mozilla Docs: https://developer.mozilla.org/en-US/docs/Web/SVG/Tutorial/Paths
Each sub-method must be implemented with the following structure:
def descriptive_name(*command_arguments):
execute calculations and transformations, **do not modify or create any instance variables**
generate curve
modify instance variables
return curve
Alternatively a sub-method may simply call a base command.
:param command_key: a character representing a specific command based on the svg standard
:param command_arguments: A list containing the arguments for the current command_key
"""
# Establish a new initial point and a new current point. (multiple coordinates are parsed as lineto commands)
def absolute_move(x, y):
self.initial_point = Vector(x, y)
self.current_point = Vector(x, y)
return None
def relative_move(dx, dy):
return absolute_move(*(self.current_point + Vector(dx, dy)))
# Draw straight line
def absolute_line(x, y):
start = self.current_point
end = Vector(x, y)
line = Line(self.transformation.apply_affine_transformation(start),
self.transformation.apply_affine_transformation(end))
self.current_point = end
return line
def relative_line(dx, dy):
return absolute_line(*(self.current_point + Vector(dx, dy)))
def absolute_horizontal_line(x):
return absolute_line(x, self.current_point.y)
def relative_horizontal_line(dx):
return absolute_horizontal_line(self.current_point.x + dx)
def absolute_vertical_line(y):
return absolute_line(self.current_point.x, y)
def relative_vertical_line(dy):
return absolute_vertical_line(self.current_point.y + dy)
def close_path():
return absolute_line(*self.initial_point)
# Draw curvy curves
def absolute_cubic_bazier(control1_x, control1_y, control2_x,
control2_y, x, y):
trans_start = self.transformation.apply_affine_transformation(
self.current_point)
trans_end = self.transformation.apply_affine_transformation(
Vector(x, y))
trans_control1 = self.transformation.apply_affine_transformation(
Vector(control1_x, control1_y))
trans_control2 = self.transformation.apply_affine_transformation(
Vector(control2_x, control2_y))
cubic_bezier = CubicBazier(trans_start, trans_end, trans_control1,
trans_control2)
self.last_control = Vector(control2_x, control2_y)
self.current_point = Vector(x, y)
return cubic_bezier
def relative_cubic_bazier(dx1, dy1, dx2, dy2, dx, dy):
return absolute_cubic_bazier(self.current_point.x + dx1,
self.current_point.y + dy1,
self.current_point.x + dx2,
self.current_point.y + dy2,
self.current_point.x + dx,
self.current_point.y + dy)
def absolute_cubic_bezier_extension(x2, y2, x, y):
start = self.current_point
control2 = Vector(x2, y2)
end = Vector(x, y)
if self.last_control:
control1 = 2 * start - self.last_control
bazier = absolute_cubic_bazier(*control1, *control2, *end)
else:
bazier = absolute_quadratic_bazier(*control2, *end)
self.current_point = start
return bazier
def relative_cubic_bazier_extension(dx2, dy2, dx, dy):
return absolute_cubic_bezier_extension(self.current_point.x + dx2,
self.current_point.y + dy2,
self.current_point.x + dx,
self.current_point.y + dy)
def absolute_quadratic_bazier(control1_x, control1_y, x, y):
trans_end = self.transformation.apply_affine_transformation(
self.current_point)
trans_new_end = self.transformation.apply_affine_transformation(
Vector(x, y))
trans_control1 = self.transformation.apply_affine_transformation(
Vector(control1_x, control1_y))
quadratic_bezier = QuadraticBezier(trans_end, trans_new_end,
trans_control1)
self.last_control = Vector(control1_x, control1_y)
self.current_point = Vector(x, y)
return quadratic_bezier
def relative_quadratic_bazier(dx1, dy1, dx, dy):
return absolute_quadratic_bazier(self.current_point.x + dx1,
self.current_point.y + dy1,
self.current_point.x + dx,
self.current_point.y + dy)
def absolute_quadratic_bazier_extension(x, y):
start = self.current_point
end = Vector(x, y)
if self.last_control:
control = 2 * start - self.last_control
bazier = absolute_quadratic_bazier(*control, *end)
else:
bazier = absolute_quadratic_bazier(*start, *end)
self.current_point = end
return bazier
def relative_quadratic_bazier_extension(dx, dy):
return absolute_quadratic_bazier_extension(
self.current_point.x + dx, self.current_point.y + dy)
# Generate EllipticalArc with center notation from svg endpoint notation.
# Based on w3.org implementation notes. https://www.w3.org/TR/SVG2/implnote.html
# Todo transformations aren't applied correctly to elliptical arcs
def absolute_arc(rx, ry, deg_from_horizontal, large_arc_flag,
sweep_flag, x, y):
end = Vector(x, y)
start = self.current_point
radii = Vector(rx, ry)
rotation_rad = math.radians(deg_from_horizontal)
if abs(start - end) == 0:
raise ValueError("start and end points can't be equal")
radii, center, start_angle, sweep_angle = formulas.endpoint_to_center_parameterization(
start, end, radii, rotation_rad, large_arc_flag, sweep_flag)
arc = EllipticalArc(center,
radii,
rotation_rad,
start_angle,
sweep_angle,
transformation=self.transformation)
self.current_point = end
return arc
def relative_arc(rx, ry, deg_from_horizontal, large_arc_flag,
sweep_flag, dx, dy):
return absolute_arc(rx, ry, deg_from_horizontal, large_arc_flag,
sweep_flag, self.current_point.x + dx,
self.current_point.y + dy)
command_methods = {
# Only move end point
'M': absolute_move,
'm': relative_move,
# Draw straight line
'L': absolute_line,
'l': relative_line,
'H': absolute_horizontal_line,
'h': relative_horizontal_line,
'V': absolute_vertical_line,
'v': relative_vertical_line,
'Z': close_path,
'z': close_path,
# Draw bazier curves
'C': absolute_cubic_bazier,
'c': relative_cubic_bazier,
'S': absolute_cubic_bezier_extension,
's': relative_cubic_bazier_extension,
'Q': absolute_quadratic_bazier,
'q': relative_quadratic_bazier,
'T': absolute_quadratic_bazier_extension,
't': relative_quadratic_bazier_extension,
# Draw elliptical arcs
'A': absolute_arc,
'a': relative_arc
}
try:
curve = command_methods[command_key](*command_arguments)
except TypeError as type_error:
warnings.warn(
f"Mis-formed input. Skipping command {command_key, command_arguments} because it caused the "
f"following error: \n{type_error}")
except ValueError as value_error:
warnings.warn(
f"Impossible geometry. Skipping curve {command_key, command_arguments} because it caused the "
f"following value error:\n{value_error}")
else:
if curve is not None:
self.curves.append(curve)
if verbose:
print(f"{command_key}{tuple(command_arguments)} -> {curve}")
