Pending release of 0.3

[SirVer]

Hi Chris,

> Are you able to feed your display widget with images from within a
> python loop in the interactive shell?
>
> ie:
>
> while True:
>     img = grab_new_image()
>     display.new_image(img)
> The issue I am having with this PyOS_InputHook, is that for me, that
> type of loop never lets the interpreter idle (even with a sleep()
> call) and thus the PyOS_InputHook never gets called, and the gui never
> updates.
This can't work as you said. PyOS_InputHook is never called. I doesn't
work in ipython -q4thread either
because the thread switch doesn't seem to occure. There are two ways
to do it
1) either call PyOS_InputHook yourself.
2) acquire your images in another thread.

I always use 2) since my image acquisition always takes place
continously in the background. This is also a way were
PyQT really shines (It also works with wxWidgets that way, but it
hurts a bit).

so your above example would look a bit like that (not tested, just
written down like that):

class WorkerThread(QThread):
   def __init__(self, display):
      self.connect(self, SIGNAL("newImage"), self.display.newImage)
      # Keep a copy of display around so that the C object doesn't get
deleted
      self.display = display

   def run(self):
      while True:
         img = grab_new_image()
         self.emit(SIGNAL("newImage"), img)

def acquire_images(display):
   t = WorkerThread(display)
   t.start()

This example should work from the interactive shell provided you
created a QApplication object so that Qt4 has the PyOS_InputHook
acquired. Just call acquire_images(display).

Cheers,
Holger


>
>
> Cheers,
>
> Chris
>
>
>
> On Fri, Nov 6, 2009 at 11:24 AM, SirVer <sir... at gmx.de> wrote:
>
> > Hi Chris,
>
> > thanks for the links! It made for some interesting reading; i wasn't
> > aware of the System Hook. But I just investigated and my Widget works
> > just fine in a pure python session as long as a QApplication object
> > has been created before. So there is no problem here, it will work
> > fine now in ipython -qt4thread and will continue to work in future
> > ipython and also in vanilla python as long as QApplication(sys.argv)
> > has been called before the window is created (which is mandatory for
> > all QT4 Applications). So no problem here.
>
> > I now try to come to a conclusion to this thread. I didn't mean to
> > start a lengthy discussion of how things should be done differently, I
> > only want to have direction how to implement this. I try to summarize
> > my thoughts:
>
> > * I am often in need to display images from a camera and annotate them
> > with some output from algorithms (for example mark detected balls in
> > my ping pong roboters images in red). For this I've written the code
> > that can be found in my gui branch.
> > * I feel that this use case is quite different from the idea of the
> > imshow() plugin. I also feel that more people than me could profit
> > from this functionality as I use it ATM.
> > * I feel that this is hard to pull off with a plugin like
> > architecture, because the annotation part will be different for all
> > backends and all individual uses. En plus, this is more a Library kind
> > of functionality, not a enduser kind like imshow().
> > * My solution works for me and uses PyQt and PyOpenGL. My experiments
> > showed me that this is the only combination that offers the drawing
> > speed I want. I understand that other approaches could be possible or
> > feasible, but I also think that for use cases like mine, this is a
> > very common approach; especially since annotating in OpenGL is so easy
> > to do with PyQt4.
> > * Please let me state again that I do not plan to corrupt or change
> > the imshow() plugin architecture which I really like. I am just of the
> > opinion that something else is needed for my use case.
>
> > Now, please note that these are my opinions and thought and not really
> > subject to discussion. What I now really need is a design decision by
> > the architect of scikit.image; which I assume to be you, stefan:
>
> > How should I contribute this code? In which module should it go or is
> > this not a direction that scikit.image should evolve in (I'd
> > understand that and instead bring this code into my pydc1394 library
> > were it would also fit).
>
> > Cheers,
> > Holger
>
> > On 5 Nov., 17:33, Chris Colbert <sccolb... at gmail.com> wrote:
> >> Here's a couple links on it Holger.
>
> >> Hopefully the scipy links work for you (its the Ipython part of the
> >> discussion). I cant get to them right now.
>
> >>http://mail.scipy.org/pipermail/ipython-dev/2009-July/005256.htmlhttp...
>
> >> On Thu, Nov 5, 2009 at 5:14 PM, SirVer <sir... at gmx.de> wrote:
>
> >> >> However, i'm afraid that your current gui may rely on ipython
> >> >> -q4thread, which is now deprecated (big mailing list discussion on
> >> >> this). So that may throw a wrench in the video portion of it, unless
> >> >> we can figure out this pyos_input hook thing.
> >> > It infact does. Chris, could you please point me at this discussion?
> >> > It is most relevant for my work.
>
> >> > Cheers,
> >> > Holger
>
> >> >> But as my previous example shows, its definately possible to fit it
> >> >> within the plugin framework.
>
> >> >> Cheers!
>
> >> >> Chris
>
> >> >> On Thu, Nov 5, 2009 at 4:56 PM, Chris Colbert <sccolb... at gmail.com> wrote:
> >> >> > So while i havent yet been able to get the pyos_inputhook thing sorted
> >> >> > out, I did time a couple loops.
>
> >> >> > For a decent sized image, we can easily get 60fps update rates, and
> >> >> > thats including the time for the numpy operations:
>
> >> >> > In [5]: img = io.imread('/home/brucewayne/Pictures/failboat_4.jpg')
>
> >> >> > In [6]: img.shape
> >> >> > Out[6]: (503, 790, 3)
>
> >> >> > In [7]: win = io.imshow(img, updateable=True)
>
> >> >> > In [8]: def test(img, win):
> >> >> >   ...:     for i in range(30):
> >> >> >   ...:         img[:] += 1
> >> >> >   ...:         win.update()
> >> >> >   ...:
> >> >> >   ...:
>
> >> >> > In [9]: %timeit test(img, win)
> >> >> > 1 loops, best of 3: 564 ms per loop
>
> >> >> > one thing to note, I bypassed the prepare_for_display() method that we
> >> >> > usually call to make sure an array is contiguous, of the right dtype,
> >> >> > etc...
> >> >> > I assume if someone wants video, they can prepare the arrays themselves.
>
> >> >> > This behavior can also be changed by the plugin writer. For this
> >> >> > example, i simply took the easy route and subclassed ImageWindow
>
> >> >> > Cheers,
>
> >> >> > Chris
>
> >> >> > On Thu, Nov 5, 2009 at 4:24 PM, Chris Colbert <sccolb... at gmail.com> wrote:
> >> >> >> I was just testing out something along these lines, but I run into the
> >> >> >> problem of the the python interpreter not considering time.sleep() as
> >> >> >> idle time, thus, it never calls PyOS_InputHook inside of for-loops. So
> >> >> >> i'm not quite sure how to get video  feed to run interactively without
> >> >> >> hacking out something like ipython -whatever thread.
>
> >> >> >> Mind you, this is not a problem with the plugin architecture, its a
> >> >> >> problem with the python interpreter...
>
> >> >> >> but maybe i can ctypes into the os_hook and call it at the end of a
> >> >> >> loop.... <evil grin>
>
> >> >> >> 2009/11/5 Stéfan van der Walt <ste... at sun.ac.za>:
>
> >> >> >>> 2009/11/5 Chris Colbert <sccolb... at gmail.com>:
> >> >> >>>> Further, these imshow() type widgets are primarily meant to be used
> >> >> >>>> from the interactive interpreter, an environment not best suited for
> >> >> >>>> real time image acquisition and display. that said, the plugin
> >> >> >>>> archiceture can most certainly be used in the method you speak of. You
> >> >> >>>> just simply have your imshow() function return the window object, and
> >> >> >>>> implement an update() or similar method that the consumer can call to
> >> >> >>>> update the image.
>
> >> >> >>> This could even be accomplished using 'imshow' only.  The
> >> >> >>> WindowManager keeps track of the single window produced, and 'imshow'
> >> >> >>> simply grabs that window and updates its current content.  I'd be
> >> >> >>> surprised if we couldn't pump out a large number of frames-per-second
> >> >> >>> that way.
>
> >> >> >>> Stéfan