Python - PyQt - matplotlib：drawRectangle 方法

Question

我正在使用 matplotlib backend_qt5agg 处理将 matplotlib 画布绘制到 qt 窗口中。用户可以在绘图上绘制矩形（matplotlib.patches.Rectangle 类型），我通过调用canvas.draw() 方法显示矩形。如果画布包含大量数据，此方法可能会很慢，我想加快速度。

寻找解决方案，我在backend_qt5agg 手册中发现存在一个名为drawRectangle(rect) 的方法。希望此方法可以仅绘制补丁而不重绘整个画布，我尝试使用矩形补丁作为输入来调用此方法。所以我打电话给canvas.drawRectangle(my_rect)，而不是打电话给canvas.draw()。这不会画任何东西。

不幸的是，backend_qt5agg 手册纯粹是记录在案的。所以我的问题是：drawRectangle 方法是如何工作的，它是否应该比重绘整个画布更好？

最小的例子（当鼠标点击并在画布内移动时显示一个矩形）（只需将self.canvas.draw() 更改为on_motion 内的self.canvas.drawRectangle(self.rect) 以测试drawRectangle 方法）：

import sys
import matplotlib
from PyQt5 import QtCore
import PyQt5.QtWidgets as QtW
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg
from matplotlib.patches import Rectangle


class MainWindow(QtW.QMainWindow):

  def __init__(self):
    super().__init__()
    self.setWindowTitle('MyWindow')
    self._main = QtW.QWidget()
    self.setCentralWidget(self._main) 

    # Set canvas properties
    self.fig = matplotlib.figure.Figure(figsize=(5,5))
    self.canvas = FigureCanvasQTAgg(self.fig)
    self.ax = self.fig.add_subplot(1,1,1)
    self.rect = Rectangle((0,0), 0.2, 0.2, color='k', fill=None, alpha=1)
    self.ax.add_patch(self.rect); self.rect.set_visible(False)
    self.canvas.draw()

    # set Qlayout properties and show window
    self.gridLayout = QtW.QGridLayout(self._main)
    self.gridLayout.addWidget(self.canvas)
    self.setLayout(self.gridLayout)
    self.show()

    # connect mouse events to canvas
    self.fig.canvas.mpl_connect('button_press_event', self.on_click)
    self.fig.canvas.mpl_connect('motion_notify_event', self.on_motion)


  def on_click(self, event):
    if event.button == 1 or event.button == 3:
    # left or right click: get the x and y coordinates
        if event.inaxes is not None:
          self.xclick = event.xdata
          self.yclick = event.ydata
          self.on_press = True

  def on_motion(self, event):
    # draw the square
    if event.button == 1 or event.button == 3 and self.on_press == True:
      if (self.xclick is not None and self.yclick is not None):
        x0, y0 = self.xclick, self.yclick
        x1, y1 = event.xdata, event.ydata
        if (x1 is not None or y1 is not None):
          self.rect.set_width(x1 - x0)
          self.rect.set_height(y1 - y0)
          self.rect.set_xy((x0, y0))
          self.rect.set_visible(True)
          self.canvas.draw() # self.canvas.drawRectangle(self.rect)


if __name__ == '__main__':
    app = QtCore.QCoreApplication.instance()
    if app is None: app = QtW.QApplication(sys.argv)
    win = MainWindow()
    app.aboutToQuit.connect(app.deleteLater)
    app.exec_()

Answer 1

您可以使用已包含在 matplotlib.widgets 中的 RectangleSelector 小部件，而不是自己添加矩形。

这是一个示例，您需要完善它并使其适应您的需求，但我希望它能让您继续前进：

import sys
import matplotlib
from PyQt5 import QtCore
import PyQt5.QtWidgets as QtW
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg
from matplotlib.widgets import RectangleSelector


class MainWindow(QtW.QMainWindow):

    def __init__(self):
        super().__init__()
        self.setWindowTitle('MyWindow')
        self._main = QtW.QWidget()
        self.setCentralWidget(self._main) 

        # Set canvas properties
        self.fig = matplotlib.figure.Figure(figsize=(5,5))
        self.canvas = FigureCanvasQTAgg(self.fig)
        self.ax = self.fig.add_subplot(1,1,1)
        self.canvas.draw()

        self.rs = RectangleSelector(self.ax, self.line_select_callback,
                                                drawtype='box', useblit=True,
                                                button=[1, 3],  # don't use middle button
                                                minspanx=5, minspany=5,
                                                spancoords='pixels',
                                                interactive=True)

        # set Qlayout properties and show window
        self.gridLayout = QtW.QGridLayout(self._main)
        self.gridLayout.addWidget(self.canvas)
        self.setLayout(self.gridLayout)
        self.show()

        # connect mouse events to canvas
        self.fig.canvas.mpl_connect('button_press_event', self.on_click)

    def on_click(self, event):
        if event.button == 1 or event.button == 3 and not self.rs.active:
            self.rs.set_active(True)
        else:
            self.rs.set_active(False)

    def line_select_callback(self, eclick, erelease):
        x1, y1 = eclick.xdata, eclick.ydata
        x2, y2 = erelease.xdata, erelease.ydata
        print("(%3.2f, %3.2f) --> (%3.2f, %3.2f)" % (x1, y1, x2, y2))
        print(" The button you used were: %s %s" % (eclick.button, erelease.button))

if __name__ == '__main__':
    app = QtCore.QCoreApplication.instance()
    if app is None: app = QtW.QApplication(sys.argv)
    win = MainWindow()
    app.aboutToQuit.connect(app.deleteLater)
    app.exec_()

参考：https://matplotlib.org/examples/widgets/rectangle_selector.html