Create a gist now

Instantly share code, notes, and snippets.

What would you like to do?
Draw Bezier curves using Python and PyQt
#!/usr/bin/env python
# -*- coding: utf-8 -*-
import sys
import math
from PyQt4 import QtGui, QtCore
def binomial(i, n):
"""Binomial coefficient"""
return math.factorial(n) / float(
math.factorial(i) * math.factorial(n - i))
def bernstein(t, i, n):
"""Bernstein polynom"""
return binomial(i, n) * (t ** i) * ((1 - t) ** (n - i))
def bezier(t, points):
"""Calculate coordinate of a point in the bezier curve"""
n = len(points) - 1
x = y = 0
for i, pos in enumerate(points):
bern = bernstein(t, i, n)
x += pos[0] * bern
y += pos[1] * bern
return x, y
def bezier_curve_range(n, points):
"""Range of points in a curve bezier"""
for i in xrange(n):
t = i / float(n - 1)
yield bezier(t, points)
class BezierDrawer(QtGui.QWidget):
"""Draw a Bezier Curve"""
def __init__(self):
super(BezierDrawer, self).__init__()
self.setGeometry(300, 300, 450, 450)
self.setWindowTitle('Bezier Curves')
def paintEvent(self, e):
qp = QtGui.QPainter()
qp.begin(self)
qp.setRenderHints(QtGui.QPainter.Antialiasing, True)
self.doDrawing(qp)
qp.end()
def doDrawing(self, qp):
blackPen = QtGui.QPen(QtCore.Qt.black, 1, QtCore.Qt.DashLine)
redPen = QtGui.QPen(QtCore.Qt.red, 1, QtCore.Qt.DashLine)
bluePen = QtGui.QPen(QtCore.Qt.blue, 1, QtCore.Qt.DashLine)
greenPen = QtGui.QPen(QtCore.Qt.green, 1, QtCore.Qt.DashLine)
redBrush = QtGui.QBrush(QtCore.Qt.red)
steps = 1000
controlPoints = (
(50, 170),
(150, 370),
(250, 35),
(400, 320))
oldPoint = controlPoints[0]
qp.setPen(redPen)
qp.setBrush(redBrush)
qp.drawEllipse(oldPoint[0] - 3, oldPoint[1] - 3, 6, 6)
qp.drawText(oldPoint[0] + 5, oldPoint[1] - 3, '1')
for i, point in enumerate(controlPoints[1:]):
i += 2
qp.setPen(blackPen)
qp.drawLine(oldPoint[0], oldPoint[1], point[0], point[1])
qp.setPen(redPen)
qp.drawEllipse(point[0] - 3, point[1] - 3, 6, 6)
qp.drawText(point[0] + 5, point[1] - 3, '%d' % i)
oldPoint = point
qp.setPen(bluePen)
for point in bezier_curve_range(steps, controlPoints):
qp.drawLine(oldPoint[0], oldPoint[1], point[0], point[1])
oldPoint = point
def main(args):
app = QtGui.QApplication(sys.argv)
ex = BezierDrawer()
ex.show()
app.exec_()
if __name__=='__main__':
main(sys.argv[1:])
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment