Hi,
I wanted to be able to select a rectangular region from the graph as
one part of a script so I combined BlockingInput and
RectangleSelector to create BlockingRectangleSelector, and the pylab
style interface function, ginput_rect
This serves my immediate needs and I'm unlikely to develop it further.
Before adding it to matplotlib a couple of changes are needed::
* Other kinds of selectors, such as span, line and lasso should be
possible
* Selectors such as RectangularSelector can be added to a set of axes
but not removed. Removing them requires unhooking the mpl_connect
callbacks, but the cid is not being saved.
* The graph wasn't always drawn before selection in ipython or before
a subsequent show() so I forced it with explicit draw_idle() calls.
This may lead to unnecessary redraws.
- Paul
# This program is public domain
# Author: Paul Kienzle
"""
Select a region of the graph.
ginput_rect(ax) selects a region from the axes and continues the script.
s = BlockingRectangleSelector(ax) adds a rectangle selector to the axes and
lets the script call s.select() whenever a new region is needed.
demo() shows the selector in action.
"""
from matplotlib.pyplot import gca
from matplotlib.widgets import RectangleSelector
from matplotlib.blocking_input import BlockingInput
class BlockingRectangleSelector:
"""
Blocking rectangle selector selects once then continues with script.
"""
def __init__(self, ax=None):
if ax is None: ax=gca()
self.ax = ax
# drawtype is 'box' or 'line' or 'none'
self.selector = RectangleSelector(self.ax, self._callback,
drawtype='box',useblit=True,
minspanx=5,minspany=5,spancoords='pixels')
self.selector.set_active(False)
self.block = BlockingInput(self.ax.figure)
def _callback(self, event1, event2):
"""
Selection callback. event1 and event2 are the press and release events
"""
x1, y1 = event1.xdata, event1.ydata
x2, y2 = event2.xdata, event2.ydata
if x1>x2: x1,x2 = x2,x1
if y1>y2: y1,y2 = y2,y1
self.x1,self.x2,self.y1,self.y2 = x1,x2,y1,y2
self.ax.figure.canvas.stop_event_loop()
def select(self):
"""
Wait for box to be selected on the axes.
"""
# Make sure the graph is drawn before select.
# This appears to be needed for ipython.
self.ax.figure.canvas.draw_idle()
# Wait for selector to complete
self.selector.set_active(True)
self.block()
self.selector.set_active(False)
# Force redraw, otherwise next show() doesn't
# update the graph.
#self.ax.figure.canvas.draw_idle()
def remove(self):
"""
Remove the selector from the axes.
Note: this currently does nothing since matplotlib doesn't allow
widgets to be removed from axes.
"""
pass # rectangle widget can't be removed from axes
def ginput_rect(ax=None):
"""
Wait for user to select a region on the axes.
Returns x1,x2,y1,y2
"""
s = BlockingRectangleSelector(ax=ax)
s.select()
s.remove()
return s.x1,s.x2,s.y1,s.y2
def demo():
# Example comes from matplotlib/examples/rectangle_selector.py
from numpy import arange, sin, cos, pi
from pylab import subplot, plot, axis, show
subplot(111)
# If N is large one can see improvement by blitting!
N=100000
x=10.0*arange(N)/(N-1)
plot(x,sin(.2*pi*x),lw=3,c='b',alpha=.7)
plot(x,cos(.2*pi*x),lw=3.5,c='r',alpha=.5)
plot(x,-sin(.2*pi*x),lw=3.5,c='g',alpha=.3)
print "\n click --> release"
x1,x2,y1,y2 = ginput_rect()
print "(%3.2f, %3.2f) --> (%3.2f, %3.2f)"%(x1,y1,x2,y2)
# Zoom in to the selected rectangle
axis([x1, x2, y1, y2])
show()
if __name__ == "__main__":
demo()
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