draggable_plot.py

# -*- coding: utf-8 -*-

import math

import matplotlib.pyplot as plt
from matplotlib.backend_bases import MouseEvent


class DraggablePlotExample(object):
 u""" An example of plot with draggable markers """

 def __init__(self):
 self._figure, self._axes, self._line = None, None, None
 self._dragging_point = None
 self._points = {}

 self._init_plot()

 def _init_plot(self):
 self._figure = plt.figure("Example plot")
 axes = plt.subplot(1, 1, 1)
 axes.set_xlim(0, 100)
 axes.set_ylim(0, 100)
 axes.grid(which="both")
 self._axes = axes

 self._figure.canvas.mpl_connect('button_press_event', self._on_click)
 self._figure.canvas.mpl_connect('button_release_event', self._on_release)
 self._figure.canvas.mpl_connect('motion_notify_event', self._on_motion)
 plt.show()

 def _update_plot(self):
 if not self._points:
 self._line.set_data([], [])
 else:
 x, y = zip(*sorted(self._points.items()))
 # Add new plot
 if not self._line:
 self._line, = self._axes.plot(x, y, "b", marker="o", markersize=10)
 # Update current plot
 else:
 self._line.set_data(x, y)
 self._figure.canvas.draw()

 def _add_point(self, x, y=None):
 if isinstance(x, MouseEvent):
 x, y = int(x.xdata), int(x.ydata)
 self._points[x] = y
 return x, y

 def _remove_point(self, x, _):
 if x in self._points:
 self._points.pop(x)

 def _find_neighbor_point(self, event):
 u""" Find point around mouse position

 :rtype: ((int, int)|None)
 :return: (x, y) if there are any point around mouse else None
 """
 distance_threshold = 3.0
 nearest_point = None
 min_distance = math.sqrt(2 * (100 ** 2))
 for x, y in self._points.items():
 distance = math.hypot(event.xdata - x, event.ydata - y)
 if distance < min_distance:
 min_distance = distance
 nearest_point = (x, y)
 if min_distance < distance_threshold:
 return nearest_point
 return None

 def _on_click(self, event):
 u""" callback method for mouse click event

 :type event: MouseEvent
 """
 # left click
 if event.button == 1 and event.inaxes in [self._axes]:
 point = self._find_neighbor_point(event)
 if point:
 self._dragging_point = point
 else:
 self._add_point(event)
 self._update_plot()
 # right click
 elif event.button == 3 and event.inaxes in [self._axes]:
 point = self._find_neighbor_point(event)
 if point:
 self._remove_point(*point)
 self._update_plot()

 def _on_release(self, event):
 u""" callback method for mouse release event

 :type event: MouseEvent
 """
 if event.button == 1 and event.inaxes in [self._axes] and self._dragging_point:
 self._dragging_point = None
 self._update_plot()

 def _on_motion(self, event):
 u""" callback method for mouse motion event

 :type event: MouseEvent
 """
 if not self._dragging_point:
 return
 if event.xdata is None or event.ydata is None:
 return
 self._remove_point(*self._dragging_point)
 self._dragging_point = self._add_point(event)
 self._update_plot()


if __name__ == "__main__":
 plot = DraggablePlotExample()