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matplotlib绘制鼠标的十字光标的实现(自定义方式,官方实例)

时间:2021-08-23 10:58     来源/作者:mighty13

matplotlib在widgets模块提供Cursor类用于支持十字光标的生成。另外官方还提供了自定义十字光标的实例。

widgets模块Cursor类源码

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class Cursor(AxesWidget):
  """
  A crosshair cursor that spans the axes and moves with mouse cursor.
 
  For the cursor to remain responsive you must keep a reference to it.
 
  Parameters
  ----------
  ax : `matplotlib.axes.Axes`
    The `~.axes.Axes` to attach the cursor to.
  horizOn : bool, default: True
    Whether to draw the horizontal line.
  vertOn : bool, default: True
    Whether to draw the vertical line.
  useblit : bool, default: False
    Use blitting for faster drawing if supported by the backend.
 
  Other Parameters
  ----------------
  **lineprops
    `.Line2D` properties that control the appearance of the lines.
    See also `~.Axes.axhline`.
 
  Examples
  --------
  See :doc:`/gallery/widgets/cursor`.
  """
 
  def __init__(self, ax, horizOn=True, vertOn=True, useblit=False,
         **lineprops):
    AxesWidget.__init__(self, ax)
 
    self.connect_event('motion_notify_event', self.onmove)
    self.connect_event('draw_event', self.clear)
 
    self.visible = True
    self.horizOn = horizOn
    self.vertOn = vertOn
    self.useblit = useblit and self.canvas.supports_blit
 
    if self.useblit:
      lineprops['animated'] = True
    self.lineh = ax.axhline(ax.get_ybound()[0], visible=False, **lineprops)
    self.linev = ax.axvline(ax.get_xbound()[0], visible=False, **lineprops)
 
    self.background = None
    self.needclear = False
 
  def clear(self, event):
    """Internal event handler to clear the cursor."""
    if self.ignore(event):
      return
    if self.useblit:
      self.background = self.canvas.copy_from_bbox(self.ax.bbox)
    self.linev.set_visible(False)
    self.lineh.set_visible(False)
    
  def onmove(self, event):
    """Internal event handler to draw the cursor when the mouse moves."""
    if self.ignore(event):
      return
    if not self.canvas.widgetlock.available(self):
      return
    if event.inaxes != self.ax:
      self.linev.set_visible(False)
      self.lineh.set_visible(False)
 
      if self.needclear:
        self.canvas.draw()
        self.needclear = False
      return
    self.needclear = True
    if not self.visible:
      return
    self.linev.set_xdata((event.xdata, event.xdata))
 
    self.lineh.set_ydata((event.ydata, event.ydata))
    self.linev.set_visible(self.visible and self.vertOn)
    self.lineh.set_visible(self.visible and self.horizOn)
 
    self._update()
 
  def _update(self):
    if self.useblit:
      if self.background is not None:
        self.canvas.restore_region(self.background)
      self.ax.draw_artist(self.linev)
      self.ax.draw_artist(self.lineh)
      self.canvas.blit(self.ax.bbox)
    else:
      self.canvas.draw_idle()
    return False

自定义十字光标实现

简易十字光标实现

首先在 Cursor类的构造方法__init__中,构造了十字光标的横线、竖线和坐标显示;然后在on_mouse_move方法中,根据事件数据更新横竖线和坐标显示,最后在调用时,通过mpl_connect方法绑定on_mouse_move方法和鼠标移动事件'motion_notify_event'。

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import matplotlib.pyplot as plt
import numpy as np
 
 
class Cursor:
  """
  A cross hair cursor.
  """
  def __init__(self, ax):
    self.ax = ax
    self.horizontal_line = ax.axhline(color='k', lw=0.8, ls='--')
    self.vertical_line = ax.axvline(color='k', lw=0.8, ls='--')
    # text location in axes coordinates
    self.text = ax.text(0.72, 0.9, '', transform=ax.transAxes)
 
  def set_cross_hair_visible(self, visible):
    need_redraw = self.horizontal_line.get_visible() != visible
    self.horizontal_line.set_visible(visible)
    self.vertical_line.set_visible(visible)
    self.text.set_visible(visible)
    return need_redraw
 
  def on_mouse_move(self, event):
    if not event.inaxes:
      need_redraw = self.set_cross_hair_visible(False)
      if need_redraw:
        self.ax.figure.canvas.draw()
    else:
      self.set_cross_hair_visible(True)
      x, y = event.xdata, event.ydata
      # update the line positions
      self.horizontal_line.set_ydata(y)
      self.vertical_line.set_xdata(x)
      self.text.set_text('x=%1.2f, y=%1.2f' % (x, y))
      self.ax.figure.canvas.draw()
 
 
x = np.arange(0, 1, 0.01)
y = np.sin(2 * 2 * np.pi * x)
 
fig, ax = plt.subplots()
ax.set_title('Simple cursor')
ax.plot(x, y, 'o')
cursor = Cursor(ax)
#关键部分,绑定鼠标移动事件处理
fig.canvas.mpl_connect('motion_notify_event', cursor.on_mouse_move)
plt.show()

优化十字光标实现

在简易实现中,每次鼠标移动时,都会重绘整个图像,这样效率比较低。
在优化实现中,每次鼠标移动时,只重绘光标和坐标显示,背景图像不再重绘。

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import matplotlib.pyplot as plt
import numpy as np
 
 
class BlittedCursor:
  """
  A cross hair cursor using blitting for faster redraw.
  """
  def __init__(self, ax):
    self.ax = ax
    self.background = None
    self.horizontal_line = ax.axhline(color='k', lw=0.8, ls='--')
    self.vertical_line = ax.axvline(color='k', lw=0.8, ls='--')
    # text location in axes coordinates
    self.text = ax.text(0.72, 0.9, '', transform=ax.transAxes)
    self._creating_background = False
    ax.figure.canvas.mpl_connect('draw_event', self.on_draw)
 
  def on_draw(self, event):
    self.create_new_background()
 
  def set_cross_hair_visible(self, visible):
    need_redraw = self.horizontal_line.get_visible() != visible
    self.horizontal_line.set_visible(visible)
    self.vertical_line.set_visible(visible)
    self.text.set_visible(visible)
    return need_redraw
 
  def create_new_background(self):
    if self._creating_background:
      # discard calls triggered from within this function
      return
    self._creating_background = True
    self.set_cross_hair_visible(False)
    self.ax.figure.canvas.draw()
    self.background = self.ax.figure.canvas.copy_from_bbox(self.ax.bbox)
    self.set_cross_hair_visible(True)
    self._creating_background = False
 
  def on_mouse_move(self, event):
    if self.background is None:
      self.create_new_background()
    if not event.inaxes:
      need_redraw = self.set_cross_hair_visible(False)
      if need_redraw:
        self.ax.figure.canvas.restore_region(self.background)
        self.ax.figure.canvas.blit(self.ax.bbox)
    else:
      self.set_cross_hair_visible(True)
      # update the line positions
      x, y = event.xdata, event.ydata
      self.horizontal_line.set_ydata(y)
      self.vertical_line.set_xdata(x)
      self.text.set_text('x=%1.2f, y=%1.2f' % (x, y))
 
      self.ax.figure.canvas.restore_region(self.background)
      self.ax.draw_artist(self.horizontal_line)
      self.ax.draw_artist(self.vertical_line)
      self.ax.draw_artist(self.text)
      self.ax.figure.canvas.blit(self.ax.bbox)
 
 
x = np.arange(0, 1, 0.01)
y = np.sin(2 * 2 * np.pi * x)
 
fig, ax = plt.subplots()
ax.set_title('Blitted cursor')
ax.plot(x, y, 'o')
blitted_cursor = BlittedCursor(ax)
fig.canvas.mpl_connect('motion_notify_event', blitted_cursor.on_mouse_move)
plt.show()

捕捉数据十字光标实现

在前面的两种实现中,鼠标十字光标可以随意移动。在本实现中,十字光标只会出现在离鼠标x坐标最近的数据点上。

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import matplotlib.pyplot as plt
import numpy as np
 
 
class SnappingCursor:
  """
  A cross hair cursor that snaps to the data point of a line, which is
  closest to the *x* position of the cursor.
 
  For simplicity, this assumes that *x* values of the data are sorted.
  """
  def __init__(self, ax, line):
    self.ax = ax
    self.horizontal_line = ax.axhline(color='k', lw=0.8, ls='--')
    self.vertical_line = ax.axvline(color='k', lw=0.8, ls='--')
    self.x, self.y = line.get_data()
    self._last_index = None
    # text location in axes coords
    self.text = ax.text(0.72, 0.9, '', transform=ax.transAxes)
 
  def set_cross_hair_visible(self, visible):
    need_redraw = self.horizontal_line.get_visible() != visible
    self.horizontal_line.set_visible(visible)
    self.vertical_line.set_visible(visible)
    self.text.set_visible(visible)
    return need_redraw
 
  def on_mouse_move(self, event):
    if not event.inaxes:
      self._last_index = None
      need_redraw = self.set_cross_hair_visible(False)
      if need_redraw:
        self.ax.figure.canvas.draw()
    else:
      self.set_cross_hair_visible(True)
      x, y = event.xdata, event.ydata
      index = min(np.searchsorted(self.x, x), len(self.x) - 1)
      if index == self._last_index:
        return # still on the same data point. Nothing to do.
      self._last_index = index
      x = self.x[index]
      y = self.y[index]
      # update the line positions
      self.horizontal_line.set_ydata(y)
      self.vertical_line.set_xdata(x)
      self.text.set_text('x=%1.2f, y=%1.2f' % (x, y))
      self.ax.figure.canvas.draw()
 
 
x = np.arange(0, 1, 0.01)
y = np.sin(2 * 2 * np.pi * x)
 
fig, ax = plt.subplots()
ax.set_title('Snapping cursor')
line, = ax.plot(x, y, 'o')
snap_cursor = SnappingCursor(ax, line)
fig.canvas.mpl_connect('motion_notify_event', snap_cursor.on_mouse_move)
plt.show()

参考资料

https://www.matplotlib.org.cn/gallery/misc/cursor_demo_sgskip.html

到此这篇关于matplotlib绘制鼠标的十字光标的实现(自定义方式,官方实例)的文章就介绍到这了,更多相关matplotlib鼠标十字光标 内容请搜索服务器之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持服务器之家!

原文链接:https://blog.csdn.net/mighty13/article/details/112346707

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