使用pyqtgraph绘制圆弧

Question

我需要使用 pyqtgraph 在屏幕上绘制一些形状。我选择 pyqtgraph 而不是 matplotlib 因为前者在存在大量形状时速度更快。对于线条多边形，一切都很好，因为我可以简单地绘制多条直线。但是我怎样才能有效地表示弧线呢？

我在这里发现函数 pyqtgraph.QtGui.QGraphicsEllipseItem() 允许我绘制一个完整的椭圆。但是，如果我只需要那个椭圆的弧怎么办？

Answer 1

您可以计算弧上某些点的位置并用 PlotCurveItem

显示它们

import pyqtgraph as pg
import numpy as np

from pyqtgraph.Qt import QtCore, QtGui

t= np.arange(0,5*2*np.pi/6 ,0.01)
x = np.sin(t+0.5)
y = np.cos(t+0.5)
win = pg.GraphicsLayoutWidget(show=True, title="Plotting")
win.setFixedSize(500, 500)
p = win.addPlot(title='')
p.setXRange(-1.5, 1.5, padding=0)
p.setYRange(-1.5, 1.5, padding=0)


c = pg.PlotCurveItem(x,y)

p.addItem(c)

if __name__ == '__main__':
    import sys
    if (sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
        QtGui.QApplication.instance().exec_()

Answer 2

这是一个解决方案，您可以将两个角的度数和圆弧的方向（顺时针或逆时针）。你也可以把半径。要平移圆弧，您只需为 x 轴和 y 轴添加两个标量即可。

import pyqtgraph as pg
import numpy as np

from pyqtgraph.Qt import QtCore, QtGui

def Get_Points(r, a1, a2, nbPoints,clockwise=True):
    a1_rad = np.radians(a1)
    if a1_rad <0:
        a1_rad += 2 * np.pi
    a2_rad = np.radians(a2)
    if a2_rad <0:
        a2_rad += 2 * np.pi

    if a1_rad > a2_rad:
        if clockwise:
            t= np.linspace( a1_rad,a2_rad, nbPoints)
        else:
            t = np.linspace(a2_rad, a1_rad - 2 * np.pi,nbPoints)
    else:
        if clockwise:
            t= np.linspace(a2_rad, a1_rad,nbPoints)
        else:
            t = np.linspace(a1_rad, a2_rad - 2 * np.pi, nbPoints)
    x = r * np.cos(t)
    y = r * np.sin(t)
    return x, y

win = pg.GraphicsLayoutWidget(show=True, title="Plotting")
win.setFixedSize(500, 500)
p = win.addPlot(title='')
r = 10
a1 = 80
a2 = -200
x,y = Get_Points(r, a1, a2, 1000,clockwise=True)

c = pg.PlotCurveItem(x,y,cl=True)
p.setXRange(-1.5 * r, 1.5 * r, padding=0)
p.setYRange(-1.5 * r, 1.5 * r, padding=0)

p.addItem(c)

if __name__ == '__main__':
    import sys
    if (sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
        QtGui.QApplication.instance().exec_()

使用pyqtgraph绘制圆弧

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