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I need to have 2 draggable points in a figureCanvas. But I have a supplementary constraint: the 2 points must be linked by a line. When I drag a point, of course (it wouldn't be funny otherwise), the line must be dynamically drawn, and still linked to the 2 points.
I managed to create the 2 draggable points, with this topic: Matplotlib drag overlapping points interactively
I modified a bit the code to use it trough a subclass of FigureCanvas (to later include the graph in a PyQt application):
import matplotlib.pyplot as plt
import matplotlib.patches as patches
class DraggablePoint:
# https://stackoverflow.com/questions/21654008/matplotlib-drag-overlapping-points-interactively
lock = None # only one can be animated at a time
def __init__(self, parent, x=0.1, y=0.1):
self.parent = parent
self.point = patches.Ellipse((x, y), 0.01, 0.03, fc='r', alpha=0.5)
self.x = x
self.y = y
parent.fig.axes[0].add_patch(self.point)
self.press = None
self.background = None
self.connect()
def connect(self):
'connect to all the events we need'
self.cidpress = self.point.figure.canvas.mpl_connect('button_press_event', self.on_press)
self.cidrelease = self.point.figure.canvas.mpl_connect('button_release_event', self.on_release)
self.cidmotion = self.point.figure.canvas.mpl_connect('motion_notify_event', self.on_motion)
def on_press(self, event):
if event.inaxes != self.point.axes: return
if DraggablePoint.lock is not None: return
contains, attrd = self.point.contains(event)
if not contains: return
self.press = (self.point.center), event.xdata, event.ydata
DraggablePoint.lock = self
# draw everything but the selected rectangle and store the pixel buffer
canvas = self.point.figure.canvas
axes = self.point.axes
self.point.set_animated(True)
canvas.draw()
self.background = canvas.copy_from_bbox(self.point.axes.bbox)
# now redraw just the rectangle
axes.draw_artist(self.point)
# and blit just the redrawn area
canvas.blit(axes.bbox)
def on_motion(self, event):
if DraggablePoint.lock is not self:
return
if event.inaxes != self.point.axes: return
self.point.center, xpress, ypress = self.press
dx = event.xdata - xpress
dy = event.ydata - ypress
self.point.center = (self.point.center[0]+dx, self.point.center[1]+dy)
canvas = self.point.figure.canvas
axes = self.point.axes
# restore the background region
canvas.restore_region(self.background)
# redraw just the current rectangle
axes.draw_artist(self.point)
# blit just the redrawn area
canvas.blit(axes.bbox)
def on_release(self, event):
'on release we reset the press data'
if DraggablePoint.lock is not self:
return
self.press = None
DraggablePoint.lock = None
# turn off the rect animation property and reset the background
self.point.set_animated(False)
self.background = None
# redraw the full figure
self.point.figure.canvas.draw()
self.x = self.point.center[0]
self.y = self.point.center[1]
def disconnect(self):
'disconnect all the stored connection ids'
self.point.figure.canvas.mpl_disconnect(self.cidpress)
self.point.figure.canvas.mpl_disconnect(self.cidrelease)
self.point.figure.canvas.mpl_disconnect(self.cidmotion)
There will only be 2 points on the future graph, and I can access the other point from the class DraggablePoint trough self.parent.
I think I need to draw a line between the 2 points, in the function on_motion. But I tried and found nothing. Do you have an idea about how to achieve that ?
286
Ok I finally found the solution. I post it here for those who might need it. This code basically allow to have 2 draggable points linked by a line. If you move one of the points, the line follows. Very useful to make a baseline in scientific applications.
import matplotlib.pyplot as plt
import matplotlib.patches as patches
from matplotlib.lines import Line2D
class DraggablePoint:
# http://stackoverflow.com/questions/21654008/matplotlib-drag-overlapping-points-interactively
lock = None # only one can be animated at a time
def __init__(self, parent, x=0.1, y=0.1, size=0.1):
self.parent = parent
self.point = patches.Ellipse((x, y), size, size * 3, fc='r', alpha=0.5, edgecolor='r')
self.x = x
self.y = y
parent.fig.axes[0].add_patch(self.point)
self.press = None
self.background = None
self.connect()
if self.parent.list_points:
line_x = [self.parent.list_points[0].x, self.x]
line_y = [self.parent.list_points[0].y, self.y]
self.line = Line2D(line_x, line_y, color='r', alpha=0.5)
parent.fig.axes[0].add_line(self.line)
def connect(self):
'connect to all the events we need'
self.cidpress = self.point.figure.canvas.mpl_connect('button_press_event', self.on_press)
self.cidrelease = self.point.figure.canvas.mpl_connect('button_release_event', self.on_release)
self.cidmotion = self.point.figure.canvas.mpl_connect('motion_notify_event', self.on_motion)
def on_press(self, event):
if event.inaxes != self.point.axes: return
if DraggablePoint.lock is not None: return
contains, attrd = self.point.contains(event)
if not contains: return
self.press = (self.point.center), event.xdata, event.ydata
DraggablePoint.lock = self
# draw everything but the selected rectangle and store the pixel buffer
canvas = self.point.figure.canvas
axes = self.point.axes
self.point.set_animated(True)
if self == self.parent.list_points[1]:
self.line.set_animated(True)
else:
self.parent.list_points[1].line.set_animated(True)
canvas.draw()
self.background = canvas.copy_from_bbox(self.point.axes.bbox)
# now redraw just the rectangle
axes.draw_artist(self.point)
# and blit just the redrawn area
canvas.blit(axes.bbox)
def on_motion(self, event):
if DraggablePoint.lock is not self:
return
if event.inaxes != self.point.axes: return
self.point.center, xpress, ypress = self.press
dx = event.xdata - xpress
dy = event.ydata - ypress
self.point.center = (self.point.center[0]+dx, self.point.center[1]+dy)
canvas = self.point.figure.canvas
axes = self.point.axes
# restore the background region
canvas.restore_region(self.background)
# redraw just the current rectangle
axes.draw_artist(self.point)
if self == self.parent.list_points[1]:
axes.draw_artist(self.line)
else:
self.parent.list_points[1].line.set_animated(True)
axes.draw_artist(self.parent.list_points[1].line)
self.x = self.point.center[0]
self.y = self.point.center[1]
if self == self.parent.list_points[1]:
line_x = [self.parent.list_points[0].x, self.x]
line_y = [self.parent.list_points[0].y, self.y]
self.line.set_data(line_x, line_y)
else:
line_x = [self.x, self.parent.list_points[1].x]
line_y = [self.y, self.parent.list_points[1].y]
self.parent.list_points[1].line.set_data(line_x, line_y)
# blit just the redrawn area
canvas.blit(axes.bbox)
def on_release(self, event):
'on release we reset the press data'
if DraggablePoint.lock is not self:
return
self.press = None
DraggablePoint.lock = None
# turn off the rect animation property and reset the background
self.point.set_animated(False)
if self == self.parent.list_points[1]:
self.line.set_animated(False)
else:
self.parent.list_points[1].line.set_animated(False)
self.background = None
# redraw the full figure
self.point.figure.canvas.draw()
self.x = self.point.center[0]
self.y = self.point.center[1]
def disconnect(self):
'disconnect all the stored connection ids'
self.point.figure.canvas.mpl_disconnect(self.cidpress)
self.point.figure.canvas.mpl_disconnect(self.cidrelease)
self.point.figure.canvas.mpl_disconnect(self.cidmotion)
How to use the DraggablePoint class, with PyQt5:
#!/usr/bin/python
# -*-coding:Utf-8 -*
import sys
import matplotlib
matplotlib.use("Qt5Agg")
from PyQt5 import QtWidgets, QtGui
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
from matplotlib.figure import Figure
# Personnal modules
from drag import DraggablePoint
class MyGraph(FigureCanvas):
"""A canvas that updates itself every second with a new plot."""
def __init__(self, parent=None, width=5, height=4, dpi=100):
self.fig = Figure(figsize=(width, height), dpi=dpi)
self.axes = self.fig.add_subplot(111)
self.axes.grid(True)
FigureCanvas.__init__(self, self.fig)
self.setParent(parent)
FigureCanvas.setSizePolicy(self,
QtWidgets.QSizePolicy.Expanding,
QtWidgets.QSizePolicy.Expanding)
FigureCanvas.updateGeometry(self)
# To store the 2 draggable points
self.list_points = []
self.show()
self.plotDraggablePoints([0.1, 0.1], [0.2, 0.2], [0.1, 0.1])
def plotDraggablePoints(self, xy1, xy2, size=None):
"""Plot and define the 2 draggable points of the baseline"""
# del(self.list_points[:])
self.list_points.append(DraggablePoint(self, xy1[0], xy1[1], size))
self.list_points.append(DraggablePoint(self, xy2[0], xy2[1], size))
self.updateFigure()
def clearFigure(self):
"""Clear the graph"""
self.axes.clear()
self.axes.grid(True)
del(self.list_points[:])
self.updateFigure()
def updateFigure(self):
"""Update the graph. Necessary, to call after each plot"""
self.draw()
if __name__ == '__main__':
app = QtWidgets.QApplication(sys.argv)
ex = MyGraph()
sys.exit(app.exec_())
I needed more points in the graph, so I modified the solution done by JPFrancoia in order to have more points connected with lines. I hope somebody else could find it usefull, so the new drag.py file reads:
# drag.py
import matplotlib.pyplot as plt
import matplotlib.patches as patches
from matplotlib.lines import Line2D
class DraggablePoint:
# http://stackoverflow.com/questions/21654008/matplotlib-drag-overlapping-points-interactively
lock = None # only one can be animated at a time
def __init__(self, parent, x=0.1, y=0.1, size=0.1):
self.parent = parent
self.point = patches.Ellipse((x, y), size, size * 3, fc='r', alpha=0.5, edgecolor='r')
self.x = x
self.y = y
parent.fig.axes[0].add_patch(self.point)
self.press = None
self.background = None
self.connect()
# if another point already exist we draw a line
if self.parent.list_points:
line_x = [self.parent.list_points[-1].x, self.x]
line_y = [self.parent.list_points[-1].y, self.y]
self.line = Line2D(line_x, line_y, color='r', alpha=0.5)
parent.fig.axes[0].add_line(self.line)
def connect(self):
'connect to all the events we need'
self.cidpress = self.point.figure.canvas.mpl_connect('button_press_event', self.on_press)
self.cidrelease = self.point.figure.canvas.mpl_connect('button_release_event', self.on_release)
self.cidmotion = self.point.figure.canvas.mpl_connect('motion_notify_event', self.on_motion)
def on_press(self, event):
if event.inaxes != self.point.axes: return
if DraggablePoint.lock is not None: return
contains, attrd = self.point.contains(event)
if not contains: return
self.press = (self.point.center), event.xdata, event.ydata
DraggablePoint.lock = self
# draw everything but the selected rectangle and store the pixel buffer
canvas = self.point.figure.canvas
axes = self.point.axes
self.point.set_animated(True)
# TODO also the line of some other points needs to be released
point_number = self.parent.list_points.index(self)
if self == self.parent.list_points[0]:
self.parent.list_points[1].line.set_animated(True)
elif self == self.parent.list_points[-1]:
self.line.set_animated(True)
else:
self.line.set_animated(True)
self.parent.list_points[point_number+1].line.set_animated(True)
canvas.draw()
self.background = canvas.copy_from_bbox(self.point.axes.bbox)
# now redraw just the rectangle
axes.draw_artist(self.point)
# and blit just the redrawn area
canvas.blit(axes.bbox)
def on_motion(self, event):
if DraggablePoint.lock is not self:
return
if event.inaxes != self.point.axes: return
self.point.center, xpress, ypress = self.press
dx = event.xdata - xpress
dy = event.ydata - ypress
self.point.center = (self.point.center[0]+dx, self.point.center[1]+dy)
canvas = self.point.figure.canvas
axes = self.point.axes
# restore the background region
canvas.restore_region(self.background)
# redraw just the current rectangle
axes.draw_artist(self.point)
point_number = self.parent.list_points.index(self)
self.x = self.point.center[0]
self.y = self.point.center[1]
# We check if the point is A or B
if self == self.parent.list_points[0]:
# or we draw the other line of the point
self.parent.list_points[1].line.set_animated(True)
axes.draw_artist(self.parent.list_points[1].line)
elif self == self.parent.list_points[-1]:
# we draw the line of the point
axes.draw_artist(self.line)
else:
# we draw the line of the point
axes.draw_artist(self.line)
#self.parent.list_points[point_number+1].line.set_animated(True)
axes.draw_artist(self.parent.list_points[point_number+1].line)
if self == self.parent.list_points[0]:
# The first point is especial because it has no line
line_x = [self.x, self.parent.list_points[1].x]
line_y = [self.y, self.parent.list_points[1].y]
# this is were the line is updated
self.parent.list_points[1].line.set_data(line_x, line_y)
elif self == self.parent.list_points[-1]:
line_x = [self.parent.list_points[-2].x, self.x]
line_y = [self.parent.list_points[-2].y, self.y]
self.line.set_data(line_x, line_y)
else:
# The first point is especial because it has no line
line_x = [self.x, self.parent.list_points[point_number+1].x]
line_y = [self.y, self.parent.list_points[point_number+1].y]
# this is were the line is updated
self.parent.list_points[point_number+1].line.set_data(line_x, line_y)
line_x = [self.parent.list_points[point_number-1].x, self.x]
line_y = [self.parent.list_points[point_number-1].y, self.y]
self.line.set_data(line_x, line_y)
# blit just the redrawn area
canvas.blit(axes.bbox)
def on_release(self, event):
'on release we reset the press data'
if DraggablePoint.lock is not self:
return
self.press = None
DraggablePoint.lock = None
# turn off the rect animation property and reset the background
self.point.set_animated(False)
point_number = self.parent.list_points.index(self)
if self == self.parent.list_points[0]:
self.parent.list_points[1].line.set_animated(False)
elif self == self.parent.list_points[-1]:
self.line.set_animated(False)
else:
self.line.set_animated(False)
self.parent.list_points[point_number+1].line.set_animated(False)
self.background = None
# redraw the full figure
self.point.figure.canvas.draw()
self.x = self.point.center[0]
self.y = self.point.center[1]
def disconnect(self):
'disconnect all the stored connection ids'
self.point.figure.canvas.mpl_disconnect(self.cidpress)
self.point.figure.canvas.mpl_disconnect(self.cidrelease)
self.point.figure.canvas.mpl_disconnect(self.cidmotion)
And the excution is done like:
import sys
import matplotlib
matplotlib.use("Qt5Agg")
from PyQt5 import QtWidgets, QtGui
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
from matplotlib.figure import Figure
# Personnal modules
from drag import DraggablePoint
class MyGraph(FigureCanvas):
"""A canvas that updates itself every second with a new plot."""
def __init__(self, parent=None, width=5, height=4, dpi=100):
self.fig = Figure(figsize=(width, height), dpi=dpi)
self.axes = self.fig.add_subplot(111)
self.axes.grid(True)
FigureCanvas.__init__(self, self.fig)
self.setParent(parent)
FigureCanvas.setSizePolicy(self,
QtWidgets.QSizePolicy.Expanding,
QtWidgets.QSizePolicy.Expanding)
FigureCanvas.updateGeometry(self)
# To store the 2 draggable points
self.list_points = []
self.show()
self.plotDraggablePoints()
def plotDraggablePoints(self, size=0.05):
"""Plot and define the 2 draggable points of the baseline"""
# del(self.list_points[:])
self.list_points.append(DraggablePoint(self, 0.1, 0.1, size))
self.list_points.append(DraggablePoint(self, 0.2, 0.2, size))
self.list_points.append(DraggablePoint(self, 0.5, 0.5, size))
self.list_points.append(DraggablePoint(self, 0.6, 0.5, size))
self.list_points.append(DraggablePoint(self, 0.7, 0.5, size))
self.updateFigure()
def clearFigure(self):
"""Clear the graph"""
self.axes.clear()
self.axes.grid(True)
del(self.list_points[:])
self.updateFigure()
def updateFigure(self):
"""Update the graph. Necessary, to call after each plot"""
self.draw()
if __name__ == '__main__':
app = QtWidgets.QApplication(sys.argv)
ex = MyGraph()
sys.exit(app.exec_())
Here is my simple solution with the additionnal feature to add or remove points. You have then a draggable segmented line with controls on points.
The code is simple despite events handling. Improvements are welcome.
import matplotlib.pyplot as plt
import matplotlib.patches as patches
from matplotlib.lines import Line2D
#------------------------------------------------
listLabelPoints = []
point_alpha_default = 0.8
mousepress = None
currently_dragging = False
current_artist = None
offset = [0,0]
n = 0
line_object = None
#------------------------------------------------
def on_press(event):
global currently_dragging
global mousepress
currently_dragging = True
if event.button == 3:
mousepress = "right"
elif event.button == 1:
mousepress = "left"
#------------------------------------------------
def on_release(event):
global current_artist, currently_dragging
current_artist = None
currently_dragging = False
#------------------------------------------------
def on_pick(event):
global current_artist, offset, n
global listLabelPoints
if current_artist is None:
current_artist = event.artist
#print("pick ", current_artist)
if isinstance(event.artist, patches.Circle):
if event.mouseevent.dblclick:
if mousepress == "right":
#print("double click right")
if len(ax.patches) > 2:
#print("\ndelete", event.artist.get_label())
event.artist.remove()
xdata = list(line_object[0].get_xdata())
ydata = list(line_object[0].get_ydata())
for i in range(0,len(xdata)):
if event.artist.get_label() == listLabelPoints[i]:
xdata.pop(i)
ydata.pop(i)
listLabelPoints.pop(i)
break
#print('--->', listLabelPoints)
line_object[0].set_data(xdata, ydata)
plt.draw()
else:
x0, y0 = current_artist.center
x1, y1 = event.mouseevent.xdata, event.mouseevent.ydata
offset = [(x0 - x1), (y0 - y1)]
elif isinstance(event.artist, Line2D):
if event.mouseevent.dblclick:
if mousepress == "left":
#print("double click left")
n = n+1
x, y = event.mouseevent.xdata, event.mouseevent.ydata
newPointLabel = "point"+str(n)
point_object = patches.Circle([x, y], radius=50, color='r', fill=False, lw=2,
alpha=point_alpha_default, transform=ax.transData, label=newPointLabel)
point_object.set_picker(5)
ax.add_patch(point_object)
xdata = list(line_object[0].get_xdata())
ydata = list(line_object[0].get_ydata())
#print('\ninit', listLabelPoints)
pointInserted = False
for i in range(0,len(xdata)-1):
#print("--> testing inclusion %s in [%s-%s]"
# %(newPointLabel, listLabelPoints[i], listLabelPoints[i+1]))
#print('----->', min(xdata[i],xdata[i+1]), '<', x, '<', max(xdata[i],xdata[i+1]))
#print('----->', min(ydata[i],ydata[i+1]), '<', y, '<', max(ydata[i],ydata[i+1]))
if x > min(xdata[i],xdata[i+1]) and x < max(xdata[i],xdata[i+1]) and \
y > min(ydata[i],ydata[i+1]) and y < max(ydata[i],ydata[i+1]) :
xdata.insert(i+1, x)
ydata.insert(i+1, y)
listLabelPoints.insert(i+1, newPointLabel)
pointInserted = True
#print("include", newPointLabel)
break
line_object[0].set_data(xdata, ydata)
#print('final', listLabelPoints)
plt.draw()
if not pointInserted:
print("Error: point not inserted")
else:
xdata = event.artist.get_xdata()
ydata = event.artist.get_ydata()
x1, y1 = event.mouseevent.xdata, event.mouseevent.ydata
offset = xdata[0] - x1, ydata[0] - y1
#------------------------------------------------
def on_motion(event):
global current_artist
if not currently_dragging:
return
if current_artist == None:
return
if event.xdata == None:
return
dx, dy = offset
if isinstance(current_artist, patches.Circle):
cx, cy = event.xdata + dx, event.ydata + dy
current_artist.center = cx, cy
#print("moving", current_artist.get_label())
xdata = list(line_object[0].get_xdata())
ydata = list(line_object[0].get_ydata())
for i in range(0,len(xdata)):
if listLabelPoints[i] == current_artist.get_label():
xdata[i] = cx
ydata[i] = cy
break
line_object[0].set_data(xdata, ydata)
elif isinstance(current_artist, Line2D):
xdata = list(line_object[0].get_xdata())
ydata = list(line_object[0].get_ydata())
xdata0 = xdata[0]
ydata0 = ydata[0]
for i in range(0,len(xdata)):
xdata[i] = event.xdata + dx + xdata[i] - xdata0
ydata[i] = event.ydata + dy + ydata[i] - ydata0
line_object[0].set_data(xdata, ydata)
for p in ax.patches:
pointLabel = p.get_label()
i = listLabelPoints.index(pointLabel)
p.center = xdata[i], ydata[i]
plt.draw()
#------------------------------------------------
def on_click(event):
global n, line_object
if event and event.dblclick:
if len(listLabelPoints) < 2:
n = n+1
x, y = event.xdata, event.ydata
newPointLabel = "point"+str(n)
point_object = patches.Circle([x, y], radius=50, color='r', fill=False, lw=2,
alpha=point_alpha_default, transform=ax.transData, label=newPointLabel)
point_object.set_picker(5)
ax.add_patch(point_object)
listLabelPoints.append(newPointLabel)
if len(listLabelPoints) == 2:
xdata = []
ydata = []
for p in ax.patches:
cx, cy = p.center
xdata.append(cx)
ydata.append(cy)
line_object = ax.plot(xdata, ydata, alpha=0.5, c='r', lw=2, picker=True)
line_object[0].set_pickradius(5)
plt.draw()
#================================================
fig, ax = plt.subplots()
ax.set_title("Double click left button to create draggable point\nDouble click right to remove a point", loc="left")
ax.set_xlim(0, 4000)
ax.set_ylim(0, 3000)
ax.set_aspect('equal')
fig.canvas.mpl_connect('button_press_event', on_click)
fig.canvas.mpl_connect('button_press_event', on_press)
fig.canvas.mpl_connect('button_release_event', on_release)
fig.canvas.mpl_connect('pick_event', on_pick)
fig.canvas.mpl_connect('motion_notify_event', on_motion)
plt.grid(True)
plt.show()
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