concentriccircles.py 文件源码

def paintEvent(self, event):
        painter = QPainter(self)
        painter.setRenderHint(QPainter.Antialiasing, self.antialiased)
        painter.translate(self.width() / 2, self.height() / 2)

        for diameter in range(0, 256, 9):
            delta = abs((self.frameNo % 128) - diameter / 2)
            alpha = 255 - (delta * delta) / 4 - diameter
            if alpha > 0:
                painter.setPen(QPen(QColor(0, diameter / 2, 127, alpha), 3))

                if self.floatBased:
                    painter.drawEllipse(QRectF(-diameter / 2.0,
                            -diameter / 2.0, diameter, diameter))
                else:
                    painter.drawEllipse(QRect(-diameter / 2,
                            -diameter / 2, diameter, diameter))