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panzoom.py
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panzoom.py
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#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Created on 2020-11-11
@author: Peter Jüstel
https://github.com/PeterJust/
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>
"""
import matplotlib.pyplot as plt
class Panzoom():
'''
Panzoom Class: Intuitively pan and zoom a plot using dragging and
mouse-wheel in python matplotlib.
Usage: Pass the figure instance to the class while instantiating the class.
It then connects to all the necessary callback functions of the
figure (overwriting pre-existing connections!). Pan by clicking and
dragging. Zoom using the mouswheel. Shift key: x-axis-only zoom.
Control key: y-axis only zoom.
Optional argument: base_scale = <scale> -> the factor by which the
figure is zoomed at one mousewheel event.
Example usage:
import matplotlib.pyplot as plt
from panzoom import Panzoom
fig1 = plt.figure()
plt.plot([0, 1, 3, 6, 7, 4, 2, 0])
panzoomer = Panzoom(fig1)
print("drag-n-drop panning and mouswheel zooming awesomeness.
Now: at your fingertips!")
Keywords: python, matplotlib, mpl, intuitive, interactive, agile, pan,
panning, drag, dragging, drag'n'drop, zoom, zooming, mouse,
mousewheel, mouse-wheel, figure, diagram, axis, axes, chart, plot
'''
# TODO: callbacks should probably check matplotlib.axes.Axes.can_zoom() and matplotlib.axes.Axes.can_pan()
# TODO: check input for sanity.
# TODO: 'ctrl' key on Apple?
def __init__(self, fig, base_scale=1.3, **kwargs):
#https://matplotlib.org/3.1.1/users/event_handling.html
#https://matplotlib.org/3.2.0/api/backend_bases_api.html#matplotlib.backend_bases.FigureCanvasBase.mpl_connect
self.fig = fig
self.ax = None
self.panningflag = 0
self.xzoom = 1
self.yzoom = 1
self.oldxy = [0, 0]
self.base_scale = base_scale
self.fig.canvas.mpl_connect('button_press_event', self.buttonZemaphore)
self.fig.canvas.mpl_connect('button_release_event', self.buttonZemaphore)
self.fig.canvas.mpl_connect('motion_notify_event', self.pan_fun)
self.fig.canvas.mpl_connect('scroll_event', self.zoom_fun)
self.fig.canvas.mpl_connect('key_press_event', self.keyZemaphore)
self.fig.canvas.mpl_connect('key_release_event', self.keyZemaphore)
self.fig.canvas.mpl_connect('figure_leave_event', self.reset_fun)
def keyZemaphore(self, event):
# changing the flags for zooming
# https://matplotlib.org/3.2.0/api/backend_bases_api.html#matplotlib.backend_bases.KeyEvent
# xaxis zoom
if (event.key == 'shift') and (event.name == 'key_press_event'):
self.yzoom = 0
elif (event.key == 'shift') and (event.name == 'key_release_event'):
self.yzoom = 1
# yaxis zoom
elif (event.key == 'control') and (event.name == 'key_press_event'):
self.xzoom = 0
elif (event.key == 'control') and (event.name == 'key_release_event'):
self.xzoom = 1
def buttonZemaphore(self, event):
# changing the flags for panning
if (event.name == 'button_press_event') and (event.button.numerator == 1):
# left-mouse button press: activate pan
self.oldxy = [event.xdata, event.ydata]
self.panningflag = 1
elif (event.name == 'button_release_event') and (event.button.numerator == 1):
# left-mouse button release: deactivate pan
self.panningflag = 0
def pan_fun(self, event):
# drag-panning the axis
# This function has to be efficient, as it is polled often.
if (self.panningflag == 1) and (event.inaxes != None):
# do pan
self.ax = event.inaxes # set the axis to work on
x, y = event.xdata, event.ydata
self.ax.set_xlim(self.ax.get_xlim() + self.oldxy[0] - x) # set new axes limits
self.ax.set_ylim(self.ax.get_ylim() + self.oldxy[1] - y)
self.ax.figure.canvas.draw() # force re-draw
def zoom_fun(self, event):
#zooming the axis
if event.inaxes != None:
# zooming makes only sense, when pointing at an axis
self.ax = event.inaxes # set the axis to work on
# get the current x and y limits
cur_xlim = self.ax.get_xlim() # tuple: (low, high)
cur_ylim = self.ax.get_ylim()
# set the range
x = event.xdata # get event x location
y = event.ydata # get event y location
if event.button == 'up':
# deal with zoom in
scale_factor = 1/self.base_scale
elif event.button == 'down':
# deal with zoom out
scale_factor = self.base_scale
else:
# deal with something that should never happen
scale_factor = 1
print("Zoom: Button sends strange signal: " + event.button)
# set new limits
if self.xzoom == 1:
# if 'control' is NOT pressed, zoom the x-axis
lower = cur_xlim[0] * scale_factor + (1-scale_factor) * x
upper = cur_xlim[1] * scale_factor + (1-scale_factor) * x
self.ax.set_xlim([lower, upper])
#self.ax.set_xlim(np.array(cur_xlim) * scale_factor + (1-scale_factor) * x) # ->more elegant, but uses numpy
if self.yzoom == 1:
# if 'shift' is NOT pressed, zoom the y-axis
lower = cur_ylim[0] * scale_factor + (1-scale_factor) * y
upper = cur_ylim[1] * scale_factor + (1-scale_factor) * y
self.ax.set_ylim([lower, upper])
self.ax.figure.canvas.draw() # force re-draw
def reset_fun(self, event):
# reset all flags
self.ax = None
self.panningflag = 0
self.xzoom = 1
self.yzoom = 1
self.oldxy = [0, 0]