Hi,
I just had to label a sequence of images with the position and scale of a moving
object. To do this I took the nice example from
http://matplotlib.sourceforge.net/users/event_handling.html (the one using
blitting) and extended to be resizeable. The extension is trivial, but it might
be useful to someone. The code is inlined at the end of this message.
Jorge
# draggable rectangle with the animation blit techniques; see
# http://www.scipy.org/Cookbook/Matplotlib/Animations
import numpy as np
import matplotlib.pyplot as plt
class DraggableResizeableRectangle:
"""
Draggable and resizeable rectangle with the animation blit techniques.
Based on example code at
http://matplotlib.sourceforge.net/users/event_handling.html
If *allow_resize* is *True* the recatngle can be resized by dragging its
lines. *border_tol* specifies how close the pointer has to be to a line for
the drag to be considered a resize operation. Dragging is still possible by
clicking the interior of the rectangle. *fixed_aspect_ratio* determines if
the recatngle keeps its aspect ratio during resize operations.
"""
lock = None # only one can be animated at a time
def __init__(self, rect, border_tol=.15, allow_resize=True,
fixed_aspect_ratio=True):
self.rect = rect
self.border_tol = border_tol
self.allow_resize = allow_resize
self.fixed_aspect_ratio = fixed_aspect_ratio
self.press = None
self.background = None
def connect(self):
'connect to all the events we need'
self.cidpress = self.rect.figure.canvas.mpl_connect(
'button_press_event', self.on_press)
self.cidrelease = self.rect.figure.canvas.mpl_connect(
'button_release_event', self.on_release)
self.cidmotion = self.rect.figure.canvas.mpl_connect(
'motion_notify_event', self.on_motion)
def on_press(self, event):
'on button press we will see if the mouse is over us and store some data'
if event.inaxes != self.rect.axes: return
if DraggableRectangle.lock is not None: return
contains, attrd = self.rect.contains(event)
if not contains: return
#print 'event contains', self.rect.xy
x0, y0 = self.rect.xy
w0, h0 = self.rect.get_width(), self.rect.get_height()
aspect_ratio = np.true_divide(w0, h0)
self.press = x0, y0, w0, h0, aspect_ratio, event.xdata, event.ydata
DraggableRectangle.lock = self
# draw everything but the selected rectangle and store the pixel buffer
canvas = self.rect.figure.canvas
axes = self.rect.axes
self.rect.set_animated(True)
canvas.draw()
self.background = canvas.copy_from_bbox(self.rect.axes.bbox)
# now redraw just the rectangle
axes.draw_artist(self.rect)
# and blit just the redrawn area
canvas.blit(axes.bbox)
def on_motion(self, event):
'on motion we will move the rect if the mouse is over us'
if DraggableRectangle.lock is not self:
return
if event.inaxes != self.rect.axes: return
x0, y0, w0, h0, aspect_ratio, xpress, ypress = self.press
self.dx = event.xdata - xpress
self.dy = event.ydata - ypress
#self.rect.set_x(x0+dx)
#self.rect.set_y(y0+dy)
self.update_rect()
canvas = self.rect.figure.canvas
axes = self.rect.axes
# restore the background region
canvas.restore_region(self.background)
# redraw just the current rectangle
axes.draw_artist(self.rect)
# blit just the redrawn area
canvas.blit(axes.bbox)
def on_release(self, event):
'on release we reset the press data'
if DraggableRectangle.lock is not self:
return
self.press = None
DraggableRectangle.lock = None
# turn off the rect animation property and reset the background
self.rect.set_animated(False)
self.background = None
# redraw the full figure
self.rect.figure.canvas.draw()
def disconnect(self):
'disconnect all the stored connection ids'
self.rect.figure.canvas.mpl_disconnect(self.cidpress)
self.rect.figure.canvas.mpl_disconnect(self.cidrelease)
self.rect.figure.canvas.mpl_disconnect(self.cidmotion)
def update_rect(self):
x0, y0, w0, h0, aspect_ratio, xpress, ypress = self.press
dx, dy = self.dx, self.dy
bt = self.border_tol
fixed_ar = self.fixed_aspect_ratio
if (not self.allow_resize or
(abs(x0+np.true_divide(w0,2)-xpress)<np.true_divide(w0,2)-bt*w0 and
abs(y0+np.true_divide(h0,2)-ypress)<np.true_divide(h0,2)-bt*h0)):
self.rect.set_x(x0+dx)
self.rect.set_y(y0+dy)
elif abs(x0-xpress)<bt*w0:
self.rect.set_x(x0+dx)
self.rect.set_width(w0-dx)
if fixed_ar:
dy = np.true_divide(dx, aspect_ratio)
self.rect.set_y(y0+dy)
self.rect.set_height(h0-dy)
elif abs(x0+w0-xpress)<bt*w0:
self.rect.set_width(w0+dx)
if fixed_ar:
dy = np.true_divide(dx, aspect_ratio)
self.rect.set_height(h0+dy)
elif abs(y0-ypress)<bt*h0:
self.rect.set_y(y0+dy)
self.rect.set_height(h0-dy)
if fixed_ar:
dx = dy*aspect_ratio
self.rect.set_x(x0+dx)
self.rect.set_width(w0-dx)
elif abs(y0+h0-ypress)<bt*h0:
self.rect.set_height(h0+dy)
if fixed_ar:
dx = dy*aspect_ratio
self.rect.set_width(w0+dx)
fig = plt.figure()
ax = fig.add_subplot(111)
rects = ax.bar(range(10), 20*np.random.rand(10))
drs = []
for rect in rects:
dr = DraggableResizeableRectangle(rect)
dr.connect()
drs.append(dr)
plt.show()