How do I use the unpack function?

[Marlin Rowley]

Thanks for the advice!
 
However, I assumed that:
 
fourbytes = pixelComponent[:4]
 
would shave that byte off the array in pixelComponent.  So that the array is smaller by one on the next iteration.  Is this not the case?
 
I'm getting weird results now..
 
-M



> Date: Thu, 15 May 2008 09:11:23 -0700> From: gherron at islandtraining.com> To: marlin_rowley at hotmail.com> CC: python-list at python.org> Subject: Re: How do I use the unpack function?> > Marlin Rowley wrote:> > All:> >> > I've got a script that runs really slow because I'm reading from a > > stream a byte at a time:> >> > // TERRIBLE> > for y in range( height ):> > for color in range(4):> > for x in range( width ):> > pixelComponent = fileIO.read(4)> > buffer = unpack("!f",pixelComponent) << unpacks ONE > > float, but we now can do something with that pixel component.> >> >> > I can speed this up dramatically if I did this:> >> > // MUCH FASTER> > for y in range( height ):> > for color in range(4):> > pixelComponent = fileIO.read(4*width) <<<<<<<<< GET a LOT more > > data from the stream into memory FIRST!!> > for x in range( width ):> > buffer = unpack( ?????? ) <<<< how do I get each float from > > the pixelComponent???> > Just carve of the first four bytes of pixelComponent on each pass > through the loop, and unpack that.> > for x in range(width):> fourbytes = pixelComponent[:4] # first 4 bytes> pixelComponent = pixelComponent[4:] # All but first four bytes> buffer = unpack("!f", fourbytes)> > > There are probably better ways overall, but this directly answers your > question.> > Gary Herron> > > >> >> > -M> > ------------------------------------------------------------------------> > With Windows Live for mobile, your contacts travel with you. Connect > > on the go. > > <http://www.windowslive.com/mobile/overview.html?ocid=TXT_TAGLM_WL_Refresh_mobile_052008> > >> > ------------------------------------------------------------------------> >> > --> > http://mail.python.org/mailman/listinfo/python-list> 
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