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71 lines
2.1 KiB
Python
Executable file
71 lines
2.1 KiB
Python
Executable file
# Name: bezier.py
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# Package: wx.lib.pdfviewer
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#
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# Purpose: Compute Bezier curves for PDF rendered using wx.DC
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# Adapted from the original source code, see below.
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#
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# Author: David Hughes dfh@forestfield.co.uk
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# Copyright: Forestfield Software Ltd
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# Licence: Public domain
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# History: Created 17 Jun 2009
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#
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# Tags: phoenix-port, documented
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#
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#----------------------------------------------------------------------------
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"""
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This module is used to compute Bezier curves for PDF rendering.
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"""
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import wx
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from vec2d import *
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def calculate_bezier(p, steps = 30):
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"""
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Calculate a bezier curve from 4 control points and return a
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list of the resulting points.
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Depends on the 2d vector class from http://www.pygame.org/wiki/2DVectorClass
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2007 Victor Blomqvist
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Released to the Public Domain
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The function uses the forward differencing algorithm described at
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http://www.niksula.cs.hut.fi/~hkankaan/Homepages/bezierfast.html
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"""
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t = 1.0 / steps
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temp = t*t
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f = p[0]
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fd = 3 * (p[1] - p[0]) * t
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fdd_per_2 = 3 * (p[0] - 2 * p[1] + p[2]) * temp
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fddd_per_2 = 3 * (3 * (p[1] - p[2]) + p[3] - p[0]) * temp * t
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fddd = fddd_per_2 + fddd_per_2
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fdd = fdd_per_2 + fdd_per_2
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fddd_per_6 = fddd_per_2 * (1.0 / 3)
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points = []
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for x in range(steps):
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points.append(f)
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f = f + fd + fdd_per_2 + fddd_per_6
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fd = fd + fdd + fddd_per_2
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fdd = fdd + fddd
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fdd_per_2 = fdd_per_2 + fddd_per_2
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points.append(f)
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return points
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def compute_points(controlpoints, nsteps=30):
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"""
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Input 4 control points as :class:`RealPoint` and convert to vec2d instances.
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compute the nsteps points on the resulting curve and return them
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as a list of :class:`Point`
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"""
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controlvectors = []
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for p in controlpoints:
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controlvectors.append(vec2d(p.x, p.y))
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pointvectors = calculate_bezier(controlvectors, nsteps)
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curvepoints = []
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for v in pointvectors:
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curvepoints.append(wx.Point(v[0], v[1]))
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return curvepoints
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