problems displaying wxBitmaps using wxPython

Question

I've been having some problems with a program that I've been writing and would appreciate some help or input. For some background, I'm using Python 2.7 and wxPython in order to do a streaming webcam client. The client gets the images from the server in its own thread, and puts them into a Queue. The GUI thread then gets those images from the Queue and converts them to a wxBitmap object. This happens every .5 seconds and works just great. I am able to save the wxBitmap object as a file so I know that everything is working properly.

The problem that I'm having is actually getting the wxBitmap object to show up on my GUI. The only thing I seem to be able to make the GUI do is display a gray rectangle where the web cam image should be.

Here is my onPaint() that is called when I want to refresh the screen:

    def onPaint(self,e):
            ## this is the function that actually draws and redraws the window
            ## to be displayed. I think it is something similar to blit()
            ## in other graphical display frameworks
            print "in onPaint"

            ## create the device context object (graphics painter)
            dc = wx.PaintDC(self)
            dc.BeginDrawing()

            ## draw the bitmap to the screen
            dc.DrawBitmap(self.imageBit,0,0,True)
            dc.EndDrawing()            

            ## test code.
            ## the following works and updates, which means that
            ## everything is being converted properly and updated.
            ## not sure why the dc won't paint it to the window. 
            self.imageBit.SaveFile("bit.bmp", wx.BITMAP_TYPE_BMP)

Simply put, I'm at a loss as to why its not working. from my research I've found that because I'm on a windows machine I needed the BeginDrawing() and EndDrawing() functions, so I added them. Still doesn't work. There are no errors or exceptions being thrown.

other questions that might help solve this issue:

• I'm updating a wxFrame object. Maybe the wxPaintDC needs to operate in another type of container to work?
• ?

Actually, maybe my __init__ function is whats holding the problem. Am I setting this up properly?

class viewWindow(wx.Frame):
    imgSizer = (480,360)
    def __init__(self, *args, **kw):
            ## this is called when an instance of this class is created
            super(viewWindow,self).__init__(*args,**kw)

            ## here is where the actual stuff inside the frame is set up.

            self.pnl = wx.Panel(self)

            ## create a button that opens up a Connection Window
            #test = wx.Button(self.pnl, label='Connection Settings')
            ## test.Bind(wx.EVT_BUTTON, self.openConnectionWindow)

            ## create the wxImage for the web cam pic
            self.image = wx.EmptyImage(self.imgSizer[0],self.imgSizer[1])

            ## create the wxBitmap so that the wxImage can be displayed
            self.imageBit = wx.BitmapFromImage(self.image)

            ## create a timer that will update the window based of frame rate
            self.timex = wx.Timer(self, wx.ID_OK)
            self.timex.Start(500)
            self.Bind(wx.EVT_TIMER, self.redraw, self.timex)

            ## need to do the following in order to display images in wxPython:
            self.Bind(wx.EVT_PAINT, self.onPaint)

            self.SetSize(self.imgSizer)
            self.SetTitle('View Window')
            self.Show()

Anyways, thanks in advance for your help.

EDIT: I solved the problem accidentally by deleting the line self.pnl = wx.Panel(self).

So apparently it was rendering properly, but the bitmap was underneath the panel. Maybe? I'm not really sure. I'm new to this whole wxPython thing.

Answer 1

That appears to be what the wxPython demo is doing too: dc.DrawBitmap. And it works on Windows! At least, that's what they do in the AlphaDrawing demo. In the DrawImage demo, they use dc.Blit(). You might try that.

However, I wonder if you couldn't do it like I did with my photo viewer. I don't use DCs to draw, but instead just use a wx.StaticBitmap that I update.