我正在使用matplotlib库创建一个绘图并在我的wxPython GUI中显示它。我正在从LIDAR仪器绘制大量数据点。问题是，我想在这个图中绘制矩形来表示有趣的区域。但是当我在与绘图相同的轴上绘制一个矩形时，整个绘图会重新绘制，这需要花费大量的时间。这是因为self.canvas.draw（），一个重新创建所有内容的函数。
代码在GUI中显示如下：
这是问题的最小工作示例。你可以通过按住鼠标右键来绘制矩形。使用左侧的按钮绘制NetCDF数据后，矩形的绘制变得非常慢。我使用ImportanceOfBeingErnest提供的示例尝试了一些blitting，但经过多次尝试后，我仍然没有设法让它工作。
要使最小工作示例有效，您必须在plot_Data（）函数下指定NetCDF文件的路径。我提供了NetCDF文件，可在此处下载：
如何在onselect函数中将self.square blit到self.canvas？
import netCDF4 as nc
import matplotlib
matplotlib.use('WXAgg')
from matplotlib.figure import Figure
from matplotlib.backends.backend_wxagg import FigureCanvasWxAgg as FigureCanvas
import matplotlib.pyplot as plt
import matplotlib.colors as colors
import matplotlib.widgets
import time
import wx
class rightPanel(wx.Panel):
def __init__(self, parent):
wx.Panel.__init__(self, parent, style=wx.SUNKEN_BORDER)
self.initiate_Matplotlib_Plot_Canvas()
self.add_Matplotlib_Widgets()
def initiate_Matplotlib_Plot_Canvas(self):
self.figure = Figure()
self.axes = self.figure.add_subplot(111)
self.colorbar = None
self.canvas = FigureCanvas(self, -1, self.figure)
self.sizer = wx.BoxSizer(wx.VERTICAL)
self.sizer.Add(self.canvas, proportion=1, flag=wx.ALL | wx.GROW)
self.SetSizer(self.sizer)
self.Fit()
self.canvas.draw()
def add_Matplotlib_Widgets(self):
self.rectangleSelector = matplotlib.widgets.RectangleSelector(self.axes, self.onselect,
drawtype="box", useblit=True,
button=[3], interactive=False
)
def onselect(self, eclick, erelease):
tstart = time.time()
x1, y1 = eclick.xdata, eclick.ydata
x2, y2 = erelease.xdata, erelease.ydata
height = y2-y1
width = x2-x1
self.square = matplotlib.patches.Rectangle((x1,y1), width,
height, angle=0.0, edgecolor='red',
fill=False
#blit=True gives Unknown property blit
)
self.axes.add_patch(self.square)
self.canvas.draw()
# =============================================================================
# self.background = self.canvas.copy_from_bbox(self.axes.bbox)
#
#
# self.canvas.restore_region(self.background)
#
# self.axes.draw_artist(self.square)
#
# self.canvas.blit(self.axes.bbox)
# =============================================================================
tend = time.time()
print("Took " + str(tend-tstart) + " sec")
def plot_Data(self):
"""This function gets called by the leftPanel onUpdatePlot. This updates
the plot to the set variables from the widgets"""
path = "C:\\Users\\TEST_DATA\\cesar_uvlidar_backscatter_la1_t30s_v1.0_20100501.nc"
nc_data = self.NetCDF_READ(path)
print("plotting......")
vmin_value = 10**2
vmax_value = 10**-5
combo_value = nc_data['perp_beta']
self.axes.clear()
plot_object = self.axes.pcolormesh(combo_value.T, cmap='rainbow',
norm=colors.LogNorm(vmin=vmin_value, vmax=vmax_value))
self.axes.set_title("Insert title here")
if self.colorbar is None:
self.colorbar = self.figure.colorbar(plot_object)
else:
self.colorbar.update_normal(plot_object)
self.colorbar.update_normal(plot_object)
print('canvas draw..............')
self.canvas.draw()
print("plotting succesfull")
###############################################################################
###############################################################################
"""BELOW HERE IS JUST DATA MANAGEMENT AND FRAME/PANEL INIT"""
###############################################################################
###############################################################################
def NetCDF_READ(self, path):
in_nc = nc.Dataset(path)
list_of_keys = in_nc.variables.keys()
nc_data = {} #Create an empty dictionary to store NetCDF variables
for item in list_of_keys:
variable_shape = in_nc.variables[item].shape
variable_dimensions = len(variable_shape)
if variable_dimensions > 1:
nc_data[item] = in_nc.variables[item][...] #Adding netCDF variables to dictonary
return nc_data
class leftPanel(wx.Panel):
def __init__(self, parent, mainPanel):
wx.Panel.__init__(self, parent)
button = wx.Button(self, -1, label="PRESS TO PLOT")
button.Bind(wx.EVT_BUTTON, self.onButton)
self.mainPanel = mainPanel
def onButton(self, event):
self.mainPanel.rightPanel.plot_Data()
class MainPanel(wx.Panel):
def __init__(self, parent):
"""Initializing the mainPanel. This class is called by the frame."""
wx.Panel.__init__(self, parent)
self.SetBackgroundColour('red')
"""Acquire the width and height of the monitor"""
width, height = wx.GetDisplaySize()
"""Split mainpanel into two sections"""
self.vSplitter = wx.SplitterWindow(self, size=(width,(height-100)))
self.leftPanel = leftPanel(self.vSplitter, self)
self.rightPanel = rightPanel(self.vSplitter)
self.vSplitter.SplitVertically(self.leftPanel, self.rightPanel,102)
class UV_Lidar(wx.Frame):
"""Uppermost class. This class contains everything and calls everything.
It is the container around the mainClass, which on its turn is the container around
the leftPanel class and the rightPanel class. This class generates the menubar, menu items,
toolbar and toolbar items"""
def __init__(self, parent, id):
print("UV-lidar> Initializing GUI...")
wx.Frame.__init__(self, parent, id, 'UV-lidar application')
self.Bind(wx.EVT_CLOSE, self.OnCloseWindow)
self.mainPanel = MainPanel(self)
def OnCloseWindow(self, event):
self.Destroy()
if __name__ == '__main__':
app = wx.App()
frame = UV_Lidar(parent=None, id=-1)
frame.Show()
print("UV-lidar> ")
print("UV-lidar> Initializing GUI OK")
app.MainLoop()
我自己找到了解决方案：
为了blit matplotlib补丁，你必须首先将补丁添加到轴。然后在轴上绘制补丁，然后您可以将补丁blit到画布上。
square = matplotlib.patches.Rectangle((x1,y1), width,
height, angle=0.0, edgecolor='red',
fill=False)
self.axes.add_patch(square)
self.axes.draw_artist(square)
self.canvas.blit(self.axes.bbox)
如果您不想使用self.canvas.draw但仍然使用具有useblit = True的matplotlib小部件，则可以将该图保存为背景图像：self.background = self.canvas.copy_from_bbox(self.axes.bbox)并稍后使用：self.canvas.restore_region(self.background)恢复它。这比绘制一切要快得多！
当使用带有useblit = True的matplotlib的RectangleSelector小部件时，它将创建另一个背景实例变量，该变量会干扰您自己的后台实例变量。要解决此问题，您必须将RectangleSelector小部件的后台实例变量设置为等于您自己的后台实例变量。但是，只有在RectangleSelector小部件不再处于活动状态后才能执行此操作。否则它会将一些绘图动画保存到背景中。因此，一旦RectangleSelector变为非活动状态，您可以使用以下命令更新其背景：self.rectangleSelector.background = self.background
必须编辑的代码如下。使用wx.CallLater(0, lambda: self.tbd(square))，以便RectangleSelector小部件的后台实例变量仅在其变为非活动状态时才更新。
def add_Matplotlib_Widgets(self):
"""Calling these instances creates another self.background in memory. Because the widget classes
restores their self-made background after the widget closes it interferes with the restoring of
our leftPanel self.background. In order to compesate for this problem, all background instances
should be equal to eachother. They are made equal in the update_All_Background_Instances(self)
function"""
"""Creating a widget that serves as the selector to draw a square on the plot"""
self.rectangleSelector = matplotlib.widgets.RectangleSelector(self.axes, self.onselect,
drawtype="box", useblit=True,
button=[3], interactive=False
)
def onselect(self, eclick, erelease):
self.tstart = time.time()
x1, y1 = eclick.xdata, eclick.ydata
x2, y2 = erelease.xdata, erelease.ydata
height = y2-y1
width = x2-x1
square = matplotlib.patches.Rectangle((x1,y1), width,
height, angle=0.0, edgecolor='red',
fill=False
#blit=True gives Unknown property blit
)
"""In order to keep the right background and not save any rectangle drawing animations
on the background, the RectangleSelector widget has to be closed first before saving
or restoring the background"""
wx.CallLater(0, lambda: self.tbd(square))
def tbd(self, square):
"""leftPanel background is restored"""
self.canvas.restore_region(self.background)
self.axes.add_patch(square)
self.axes.draw_artist(square)
self.canvas.blit(self.axes.bbox)
"""leftPanel background is updated"""
self.background = self.canvas.copy_from_bbox(self.axes.bbox)
"""Setting all backgrounds equal to the leftPanel self.background"""
self.update_All_Background_Instances()
print('Took '+ str(time.time()-self.tstart) + ' s')
def update_All_Background_Instances(self):
"""This function sets all of the background instance variables equal
to the lefPanel self.background instance variable"""
self.rectangleSelector.background = self.background