使用 wxpython 从数据流中实时绘制轨迹

Question

我想用 wxpython 实时显示随机游走的轨迹。但是，面板最后只更新一次，显示整个随机游走，而不是逐步更新并显示时间进程。

我的第一个想法是使用 wx.ClientDC().DrawPoint() 但结果如上文所述，我没有看到正在绘制的单个点，但只显示了最终结果。

所以我考虑使用 wx.MemoryDC 将轨迹绘制到存储在内存中的位图上，然后使用 wx.ClientDC.DrawBitmap() 以设定的时间间隔将缓冲的图像复制到屏幕上，以防翻转图像瓶颈。结果还是一样，希望对你有所帮助。

本练习的目的是用来自眼动仪的位置数据替换随机游走，帧频为 1000 Hz，我希望能够尽可能接近实时地可视化轨迹（显示器的帧率为 120Hz）。

这是我的代码（大部分来自here）：

import wx
import random
import time
from time import asctime

#-------------------------------------------------------------------

def jmtime():
    return '[' + asctime()[11:19] + '] '

#-------------------------------------------------------------------
class MyDrawingArea(wx.Window):

    def __init__(self, parent, id):
        sty = wx.NO_BORDER
        wx.Window.__init__(self, parent, id, style=sty)
        self.parent = parent
        self.SetBackgroundColour(wx.WHITE)
        self.SetCursor(wx.CROSS_CURSOR)

        # Some initalisation, just to reminds the user that a variable
        # called self.BufferBmp exists. See self.OnSize().
        self.BufferBmp = None

        wx.EVT_SIZE(self, self.OnSize)
        wx.EVT_PAINT(self, self.OnPaint)
        wx.EVT_LEFT_DOWN(self,self.OnClick)

    def OnSize(self, event):
        print jmtime() + 'OnSize in MyDrawingArea'
        # Get the size of the drawing area in pixels.
        self.wi, self.he = self.GetSizeTuple()
        # Create BufferBmp and set the same size as the drawing area.
        self.BufferBmp = wx.EmptyBitmap(self.wi, self.he)
        memdc = wx.MemoryDC()
        memdc.SelectObject(self.BufferBmp)
        # Drawing job
        ret = self.DoSomeDrawing(memdc)
        if not ret:  #error
            self.BufferBmp = None
            wx.MessageBox('Error in drawing', 'CommentedDrawing', wx.OK | wx.ICON_EXCLAMATION)


    def OnPaint(self, event):
        print jmtime() + 'OnPaint in MyDrawingArea'
        dc = wx.PaintDC(self)
        dc.BeginDrawing()
        if self.BufferBmp != None:
            print jmtime() + '...drawing'
            dc.DrawBitmap(self.BufferBmp, 0, 0, True)
        else:
            print jmtime() + '...nothing to draw'
        dc.EndDrawing()



    def OnClick(self,event):
        pos = event.GetPosition()
        dc = wx.ClientDC(self)
        dc.SetPen(wx.Pen(wx.BLACK,1,wx.SOLID))

        dcwi, dche = dc.GetSizeTuple()
        x = pos.x
        y = pos.y
        time_start = time.time()

        memdc = wx.MemoryDC()
        memdc.SelectObject(self.BufferBmp)
        memdc.SetPen(wx.Pen(wx.BLACK,1,wx.SOLID))
        count = 1
        runtime = 5
        while (time.time() - time_start) < runtime:
            x,y = random_walk(x,y,dcwi,dche)
            memdc.DrawPoint(x,y)
            if (time.time() - time_start) > count * runtime * 0.1:
                print jmtime() + 'Random walk in MyDrawingArea'
                count += 1
                dc.BeginDrawing()
                dc.DrawBitmap(self.BufferBmp, 0, 0, True)
                dc.EndDrawing()
        dc.BeginDrawing()        
        dc.DrawBitmap(self.BufferBmp, 0, 0, True)
        dc.EndDrawing()

    # End of def OnClick

    def DoSomeDrawing(self, dc):
        try:
            print jmtime() + 'DoSomeDrawing in MyDrawingArea'

            dc.BeginDrawing()

            #~ raise OverflowError #for test

            # Clear everything
            dc.SetBrush(wx.Brush(wx.WHITE, wx.SOLID))
            dc.Clear()

            dc.EndDrawing()
            return True

        except:
            return False

#-------------------------------------------------------------------

class MyPanel(wx.Panel):

    def __init__(self, parent, id):
        wx.Panel.__init__(self, parent, id, wx.DefaultPosition, wx.DefaultSize)

        self.drawingarea = MyDrawingArea(self, -1)

        self.SetAutoLayout(True)

        gap = 30 #in pixels
        lc = wx.LayoutConstraints()
        lc.top.SameAs(self, wx.Top, gap)
        lc.left.SameAs(self, wx.Left, gap)
        lc.right.SameAs(self, wx.Width, gap)
        lc.bottom.SameAs(self, wx.Bottom, gap)
        self.drawingarea.SetConstraints(lc)

#-------------------------------------------------------------------

# Usual frame. Can be resized, maximized and minimized.
# The frame contains one panel.
class MyFrame(wx.Frame):

    def __init__(self, parent, id):
        wx.Frame.__init__(self, parent, id, 'CommentedDrawing', wx.Point(0, 0), wx.Size(500, 400))
        self.panel = MyPanel(self, -1)

        wx.EVT_CLOSE(self, self.OnCloseWindow)

    def OnCloseWindow(self, event):
        print jmtime() + 'OnCloseWindow in MyFrame'
        self.Destroy()

#-------------------------------------------------------------------

class MyApp(wx.App):

    def OnInit(self):
        frame = MyFrame(None, -1)
        frame.Show(True)
        self.SetTopWindow(frame)
        return True

#-------------------------------------------------------------------

def random_walk(x,y,sizex = 250, sizey = 200):

    rn = random.randrange(0,2)
    x_new = x + (1-rn) - rn
    while x_new < 0 or x_new > sizex:
        rn = random.randrange(0,2)
        x_new = x + (1-rn) - rn

    rn = random.randrange(0,2)
    y_new = y + (1-rn) - rn
    while y_new < 0 or y_new > sizex:
        rn = random.randrange(0,2)
        y_new = y + (1-rn) - rn

    return x_new, y_new

# end of def random_walk

#-------------------------------------------------------------------

def main():
    print 'main is running...'
    app = MyApp(0)
    app.MainLoop()

#-------------------------------------------------------------------

if __name__ == "__main__" :
    main()

#eof-------------------------------------------------------------------

Answer 1

这是我想出的解决方案。我没有使用 dc.DrawBitmap() 将缓冲图像复制到屏幕上，而是使用 Update() 和 Refresh() 来触发绘制事件。但是，我仍然不明白为什么我不能使用 DrawBitmap() 来完成同样的事情。

唯一的区别是 OnPaint() 使用 PaintDC() 而在 OnClick() 中我使用 ClientDC()。

无论如何，这是我当前的 OnClick() 代码：

def OnClick(self,event):
    pos = event.GetPosition()
    x = pos.x
    y = pos.y
    time_start = time.time()

    memdc = wx.MemoryDC()
    memdc.SelectObject(self.BufferBmp)
    dcwi, dche = memdc.GetSizeTuple()
    memdc.SetPen(wx.Pen(wx.BLACK,1,wx.SOLID))
    runtime = 10
    while (time.time() - time_start) < runtime:
        x,y = random_walk(x,y,dcwi,dche)
        memdc.SelectObject(self.BufferBmp)
        memdc.DrawPoint(x,y)
        memdc.SelectObject(wx.NullBitmap)
        self.Update()
        self.Refresh()
    print jmtime() + 'Random walk in MyDrawingArea done'