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Add documentation and example code

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This commit is contained in:
Matthias Neeracher 2022-03-06 05:48:15 +01:00
parent c07dee1dd5
commit dc45f27141
1 changed files with 40 additions and 0 deletions
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svgturtle.py Normal file → Executable file
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@ -1,20 +1,27 @@
#!/usr/bin/env python3
"""svgturtle - simple library to generate SVG paths from turtle graphics style commands"""
import math import math
import sys import sys
class SvgTurtle(): class SvgTurtle():
def __init__(self, homex=0, homey=0): def __init__(self, homex=0, homey=0):
"""Create a new turtle at the given home location, facing right"""
self.homex = homex self.homex = homex
self.homey = homey self.homey = homey
self.cvtangle = math.tau/360 self.cvtangle = math.tau/360
self.reset() self.reset()
def penup(self): def penup(self):
"""Subsequent movements will be invisible and only affect location and heading"""
self.pen = False self.pen = False
def pendown(self): def pendown(self):
"""Subsequent movements will be visible and drawn"""
self.pen = True self.pen = True
def forward(self, distance): def forward(self, distance):
"""Move forward"""
if self.pen and (self.path == ''): if self.pen and (self.path == ''):
self.path = "M %.2f,%.2f" % (self.x,self.y) self.path = "M %.2f,%.2f" % (self.x,self.y)
dx = distance*math.cos(self.heading) dx = distance*math.cos(self.heading)
@ -32,15 +39,22 @@ class SvgTurtle():
self.path += " m %.2f, %.2f" % (dx, dy) self.path += " m %.2f, %.2f" % (dx, dy)
def back(self, distance): def back(self, distance):
"""Move backward"""
self.forward(-distance) self.forward(-distance)
def left(self, angle): def left(self, angle):
"""Turn left by angle specified in degrees"""
self.right(-angle) self.right(-angle)
def right(self, angle): def right(self, angle):
"""Turn right by angle specified in degrees"""
self.heading = (self.heading + angle*self.cvtangle) % math.tau self.heading = (self.heading + angle*self.cvtangle) % math.tau
def circle(self, radius, extent=360, steps=None): def circle(self, radius, extent=360, steps=None):
"""Draw a circle or arc spanning extent degrees around a center
radius units to the left (if radius is positive) or right
(if radius is negative). Use a polygon if steps is specified,
otherwise a circle."""
if steps: if steps:
w = 1.0*extent/steps w = 1.0*extent/steps
w2 = 0.5*w w2 = 0.5*w
@ -76,9 +90,11 @@ class SvgTurtle():
def to_s(self): def to_s(self):
"""Return the generated path, suitable for the d attribute of an SVG <path> element"""
return self.path return self.path
def home(self): def home(self):
"""Reset to the initial position and heading"""
self.x = self.homex self.x = self.homex
self.y = self.homey self.y = self.homey
self.heading = 0 self.heading = 0
@ -86,6 +102,30 @@ class SvgTurtle():
self.path += " M %.2f, %.2f" % (self.x, self.y) self.path += " M %.2f, %.2f" % (self.x, self.y)
def reset(self): def reset(self):
"""Clear the path and return home"""
self.path = '' self.path = ''
self.pen = True self.pen = True
self.home() self.home()
if __name__ == "__main__":
turtle = SvgTurtle(50, 100)
turtle.left(90)
turtle.forward(50)
turtle.left(30)
turtle.forward(50)
turtle.penup()
turtle.back(50)
turtle.right(60)
turtle.pendown()
turtle.forward(50)
turtle.penup()
turtle.back(50)
turtle.left(30)
turtle.back(50)
turtle.right(90)
turtle.forward(70)
turtle.pendown()
turtle.circle(25)
print('<svg viewBox="0 0 170 110" xmlns="http://www.w3.org/2000/svg">')
print('<path fill="none" stroke="blue" d="%s"/>' % turtle.to_s())
print('</svg>')