When you do pixeldata[::-1,:,::-1], you just got a new array with different strides, but now non-contiguous... So I believe you really need a fresh copy of the data... tostring() copies, but could be slow... try to use
revpixels = pixeldata[::-1,:,::-1].copy() ... rgbBMP = wx.BitmapFromBuffer(640, 480, buffer(revpixels)) Perhaps you could optimize this by declaring revpixels outside de loop, and then inside de loop doing revpixels[...] = pixeldata[::-1,:,::-1] This way you will save the mem allocation of revpixels at each step of the loop. On Tue, Feb 24, 2009 at 9:15 PM, Chris Colbert <sccolb...@gmail.com> wrote: > Hi all, > > I'm new to mailing list and relatively new (~1 year) to python/numpy. I > would appreciate any insight any of you may have here. The last 8 hours of > digging through the docs has left me, finally, stuck. > > I am making a wxPython program that includes webcam functionality. The > script below just brings up a simple display window that shows the webcam > feed. The problem I am running into is in the WebCamWorker.run() method. > This method reads the raw pixel data (in string form) from the webcam > buffer. This data (thank you microsoft!) comes in BGR and bottom-to-top. I > feed this buffer to the array constructor and then swap the pixel order to > RGB and top-to-bottom. This all happens very fast, ~1ms on a Quad Core, and > the majority of that time is spent constructing the array (the numpy pixel > swapping is on the order of E-5s !). The tostring() method, however, takes a > whopping 10ms to execute. Unfortunately, the wx.BitmapFromBuffer needs a > single segment buffer interface as an argument. Is there a way to expose my > numpy array as a buffer to cut down on this conversion time? > > I have tried sending the array to the PIL Image.fromarray(), but that > eventually requires me to do a Image.tostring() anyway, which negates any > benefit. > > Thanks in advance for the help! > > S. Chris Colbert > Rehabilitation Robotics Laboratory > University of South Florida > > > #### Code ####### > > import VideoCapture > import wx > import time > import threading > import numpy as np > import Image > > > class WebCamWorker(threading.Thread): > _abort = 0 > > def __init__(self, parent): > super(WebCamWorker, self).__init__() > > self._parent = parent > self.panel = wx.Panel(parent) > > def run(self): > > while not self._abort: > > #numpy arrays reverse pixel data that comes in from CCD as BGR > and bottom to top > > pixeldata = np.ndarray((480,640,3), > buffer=webcam.getBuffer()[0], dtype='u1') > revpixels = pixeldata[::-1,:,::-1].tostring() #tostring is > an order of magnitude slower than the entire array manipulation. need a > faster method. > > rgbBMP = wx.BitmapFromBuffer(640, 480, revpixels) > dc = wx.ClientDC(self.panel) > dc.DrawBitmap(rgbBMP, 0, 0) > #b = time.clock() > #print b-a > time.sleep(0.015) > > > return > > > > class TestWxWebCam(wx.Frame): > def __init__(self, parent): > wx.Frame.__init__(self, parent, -1, size=(640,480)) > > self.worker = WebCamWorker(self) > self.worker.start() > > > > class TestApp(wx.App): > def OnInit(self): > self.frame = TestWxWebCam(None) > self.frame.Show() > > return True > > def OnExit(self): > WebCamWorker._abort = 1 #this is a hack > > > if __name__ == '__main__': > webcam = VideoCapture.Device() > webcam.setResolution(640, 480) > webcam.displayCapturePinProperties() > app = TestApp() > app.MainLoop() > del webcam > > > ### /Code ###### > > _______________________________________________ > Numpy-discussion mailing list > Numpy-discussion@scipy.org > http://projects.scipy.org/mailman/listinfo/numpy-discussion > > -- Lisandro Dalcín --------------- Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC) Instituto de Desarrollo Tecnológico para la Industria Química (INTEC) Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) PTLC - Güemes 3450, (3000) Santa Fe, Argentina Tel/Fax: +54-(0)342-451.1594 _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
