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# Alquimista/bezdraw.py forked from jl2/bezdraw.py Created Oct 9, 2011

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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:])