矩形選擇器在縮放時消失

Question

當我運行this示例並創建矩形選區時，如果我縮放或移動圍繞選區的繪圖窗口消失，直到我取消選擇移動或縮放工具並再次單擊繪圖窗口。

我在IPython筆記本中使用%matplotlib tkinter。

我已經嘗試掛鉤到時被放大窗口發生的界限更改和設置矩形選擇可見：

def persist_rect(newlims): 
    rs = toggle_selector.RS 
    print(rs.visible) 
    rs.set_visible(True) 
    rs.update() 

current_ax.callbacks.connect('xlim_changed', persist_rect) 
current_ax.callbacks.connect('ylim_changed', persist_rect) 

但是，這似乎並沒有做任何事情。它甚至不會出現toggle_selector.RS.visible被設置爲false。

我也一直在尋找source for RectangleSelector，但我還沒有看到任何啓發。

我也發現，當我使用RectangleSelector.extents = new_extents修改所選區域的範圍時，我遇到了這個問題。當例如使用滑塊小部件修改.extents時，所選區域消失，直到再次單擊該圖。

如果RectangleSelector用useblit=False作爲@ImportanceOfBeingErnest的建議進行初始化，所有這些問題都會消失，但正如他們所說，這不是一個非常好的解決方案。

Answer 1

添加回調draw_event S：

def mycallback(event): 
    if RS.active: 
     RS.update() 
plt.connect('draw_event', mycallback) 

使縮放或平移後的RectangleSelector堅持，並與useblit=True兼容。

---

例如，使用code from the docs作爲基礎：

from __future__ import print_function 
from matplotlib.widgets import RectangleSelector 
import numpy as np 
import matplotlib.pyplot as plt 
import matplotlib.widgets as widgets 
import threading 
import datetime as DT 

def line_select_callback(eclick, erelease): 
    'eclick and erelease are the press and release events' 
    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)) 

def toggle_selector(event): 
    print(' Key pressed: {}'.format(event.key)) 
    if event.key in ['D', 'd'] and RS.active: 
     print(' RectangleSelector deactivated.') 
     RS.set_active(False) 
     RS.set_visible(False) 
     RS.update() 
    if event.key in ['A', 'a'] and not RS.active: 
     print(' RectangleSelector activated.') 
     RS.set_active(True) 
     RS.set_visible(True) 
     RS.update() 

def mycallback(event): 
    if RS.active: 
     # print('mycallback') 
     RS.update() 

# def persist_rect(newlims): 
#  print('persist_rect') 
#  RS.set_visible(True) 
#  RS.update() 

fig, ax = plt.subplots() 
# figtype = type(fig) 
# figtype._draw = figtype.draw 
# def mydraw(self, renderer): 
#  print('figure.draw') 
#  self._draw(renderer) 
# figtype.draw = mydraw 

N = 100000    
x = np.linspace(0.0, 10.0, N) 

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

plt.plot(x, +np.sin(.2*np.pi*x), lw=3.5, c='b', alpha=.7) 
plt.plot(x, +np.cos(.2*np.pi*x), lw=3.5, c='r', alpha=.5) 
plt.plot(x, -np.sin(.2*np.pi*x), lw=3.5, c='g', alpha=.3) 

plt.connect('key_press_event', toggle_selector) 
plt.connect('draw_event', mycallback) 
# ax.callbacks.connect('xlim_changed', persist_rect) 
# ax.callbacks.connect('ylim_changed', persist_rect) 

plt.show() 

---

爲什麼mycallback工作，但persist_rect不？

如果取消註釋上面的註釋的語句，你會得到一些打印輸出將看起來就象這樣：

figure.draw 
mycallback 
figure.draw 
mycallback 
(4.09, -0.53) --> (8.15, 0.38) 
The button you used were: 1 1 
persist_rect 
persist_rect 
figure.draw 
mycallback 
Key pressed: q 

注意persist_rect被figure.draw之前調用，而mycallback是後來被稱爲。 figure.draw不繪製RectangleSelection，但它確實繪製了用於背景的Rectangle。所以figure.draw模糊RectangleSelection。 因此persist_rect暫時顯示RectangleSelection，但它未能堅持。 mycallback因爲在figure.draw之後被調用。

Answer 2

如果我理解正確，矩形選擇器應該在整個平移或縮放過程中保持可見。這可以通過不使用位圖傳輸來實現，

toggle_selector.RS = RectangleSelector(ax, ..., useblit=False, ...) 

這樣做的副作用是，繪圖速度可能會變慢視情節的複雜性，因爲沒有塊傳輸，完整的情節不斷重繪同時使用矩形選擇。

Answer 3

在用於RectangularSelector源代碼中的釋放方法（line 2119） 處理選擇器的能見度

def _release(self, event): 
"""on button release event""" 
    if not self.interactive: 
     self.to_draw.set_visible(False) 

子類RectangleSelector使用doc例如

修改釋放方法

class visibleRectangleSelector(RectangleSelector): 
    def release(self, event): 
     super(visibleRectangleSelector, self).release(event) 
     self.to_draw.set_visible(True) 
     self.canvas.draw() ##updates canvas for new selection 

示例代碼

from __future__ import print_function 
""" 
Do a mouseclick somewhere, move the mouse to some destination, release 
the button. This class gives click- and release-events and also draws 
a line or a box from the click-point to the actual mouseposition 
(within the same axes) until the button is released. Within the 
method 'self.ignore()' it is checked whether the button from eventpress 
and eventrelease are the same. 

""" 
from matplotlib.widgets import RectangleSelector 
import numpy as np 
import matplotlib.pyplot as plt 


class visibleRectangleSelector(RectangleSelector): 
    def release(self, event): 
     super(visibleRectangleSelector, self).release(event) 
     self.to_draw.set_visible(True) 
     self.canvas.draw() 


def line_select_callback(eclick, erelease): 
    'eclick and erelease are the press and release events' 
    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)) 


def toggle_selector(event): 
    print(' Key pressed.') 
    if event.key in ['Q', 'q'] and toggle_selector.RS.active: 
     print(' RectangleSelector deactivated.') 
     toggle_selector.RS.set_active(False) 
    if event.key in ['A', 'a'] and not toggle_selector.RS.active: 
     print(' RectangleSelector activated.') 
     toggle_selector.RS.set_active(True) 


fig, current_ax = plt.subplots() # make a new plotting range 
N = 100000 # If N is large one can see 
x = np.linspace(0.0, 10.0, N) # improvement by use blitting! 

plt.plot(x, +np.sin(.2 * np.pi * x), lw=3.5, c='b', alpha=.7) # plot something 
plt.plot(x, +np.cos(.2 * np.pi * x), lw=3.5, c='r', alpha=.5) 
plt.plot(x, -np.sin(.2 * np.pi * x), lw=3.5, c='g', alpha=.3) 

print("\n  click --> release") 

# drawtype is 'box' or 'line' or 'none' 
toggle_selector.RS = RectangleSelector(
    current_ax, 
    line_select_callback, 
    drawtype='box', 
    useblit=False, 
    button=[1, 3], # don't use middle button 
    minspanx=5, 
    minspany=5, 
    spancoords='pixels', 
    interactive=True) 
plt.connect('key_press_event', toggle_selector) 
plt.show()