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2.7.9: PhotoImage get/put

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  2.7.9: PhotoImage get/put Randy Day <randy.day@sasktel.netx> - 2015-10-20 16:05 -0600
    Re: 2.7.9: PhotoImage get/put Emile van Sebille <emile@fenx.com> - 2015-10-20 15:25 -0700
      Re: 2.7.9: PhotoImage get/put Randy Day <randy.day@sasktel.netx> - 2015-10-20 23:59 -0600
    Re: 2.7.9: PhotoImage get/put C Smith <illusiontechniques@gmail.com> - 2015-10-20 18:44 -0700
      Re: 2.7.9: PhotoImage get/put Randy Day <randy.day@sasktel.netx> - 2015-10-20 23:50 -0600
        Re: 2.7.9: PhotoImage get/put Terry Reedy <tjreedy@udel.edu> - 2015-10-21 03:51 -0400
          Re: 2.7.9: PhotoImage get/put Randy Day <randy.day@sasktel.netx> - 2015-10-21 09:31 -0600

#97846 — 2.7.9: PhotoImage get/put

I'm writing a simple image manipulation 
on a PhotoImage (tkinter), and running 
into an odd problem. The code below works, 
except for one thing:

As the image is scanned, I'd like to 
observe the pixels getting inverted on 
the image (as a kind of progress bar). 
What happens is that the code runs the 
complete loop before refreshing the 
photo. I've tried various forms of 
refresh(), update(), etc., within the 
loop, but so far no luck. Am I 
missing something simple?

def process(): # Ordinarily this would be process(photo,wdth,hgt) 
  global wdth # but I ran into problems calling it from a button 
  global hgt  #command with parameters... 
  global photo # the PhotoImage displayed by the calling code

# indents set to 1 to avoid word wrap

# Loop through rows and columns of the image 
  v=wdth 
  z=0 
  a=-1 
  for y in range (0,hgt): 
    w=v 
    v=z # swap v and z so rows are scanned l/r r/l l/r 
    z=w 
    a=-a # set our inc/dec step for lr->rl scan

    for x in range(v,z,a): 
     pix = photo.get(x,y) if pix == u'0 0 0' :
     #pixel_turn_on() 
     photo.put("#%02x%02x%02x" % (255,255,255), (x,y)) 	
    else: 
     #pixel_turn_off() 
     photo.put("#%02x%02x%02x" % (0,0,0), (x,y))

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#97847

On 10/20/2015 3:05 PM, Randy Day wrote:
> I'm writing a simple image manipulation
> on a PhotoImage (tkinter), and running
> into an odd problem. The code below works,
> except for one thing:
>
> As the image is scanned, I'd like to
> observe the pixels getting inverted on
> the image (as a kind of progress bar).
> What happens is that the code runs the
> complete loop before refreshing the
> photo.

I have no idea why, but here are some ideas I'd try out.

So is it refreshing upon completion of the loop, or upon exit from 
process()?

What happens if you put an outer loop around yours to process hght in 
ten (pick a number) steps?

Emile


> I've tried various forms of
> refresh(), update(), etc., within the
> loop, but so far no luck. Am I
> missing something simple?
>
> def process(): # Ordinarily this would be process(photo,wdth,hgt)
>    global wdth # but I ran into problems calling it from a button
>    global hgt  #command with parameters...
>    global photo # the PhotoImage displayed by the calling code
>
> # indents set to 1 to avoid word wrap
>
> # Loop through rows and columns of the image
>    v=wdth
>    z=0
>    a=-1
>    for y in range (0,hgt):
>      w=v
>      v=z # swap v and z so rows are scanned l/r r/l l/r
>      z=w
>      a=-a # set our inc/dec step for lr->rl scan
>
>      for x in range(v,z,a):
>       pix = photo.get(x,y) if pix == u'0 0 0' :
>       #pixel_turn_on()
>       photo.put("#%02x%02x%02x" % (255,255,255), (x,y)) 	
>      else:
>       #pixel_turn_off()
>       photo.put("#%02x%02x%02x" % (0,0,0), (x,y))
>
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>

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#97855

In article <mailman.63.1445379941.878.python-list@python.org>, 
emile@fenx.com says...

[snip]

> I have no idea why, but here are some ideas I'd try out.
 
> So is it refreshing upon completion of the loop, or upon exit from 
> process()?

It turns out I need to call root.update_idletasks()
for my root Tk object to get it to refresh after
I put the pixel.

It works great now.

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#97851

>> def process(): # Ordinarily this would be process(photo,wdth,hgt)
>>    global wdth # but I ran into problems calling it from a button
If you want to pass arguments to a command called when a button is
clicked, you have to use 'lambda' in tkinter.

>>    global hgt  #command with parameters...
>>    global photo # the PhotoImage displayed by the calling code
>>
>> # indents set to 1 to avoid word wrap
>>
>> # Loop through rows and columns of the image
>>    v=wdth
>>    z=0
>>    a=-1
>>    for y in range (0,hgt):
>>      w=v
>>      v=z # swap v and z so rows are scanned l/r r/l l/r
>>      z=w
>>      a=-a # set our inc/dec step for lr->rl scan
>>
>>      for x in range(v,z,a):
>>       pix = photo.get(x,y) if pix == u'0 0 0' :
>>       #pixel_turn_on()
>>       photo.put("#%02x%02x%02x" % (255,255,255), (x,y))
>>      else:
>>       #pixel_turn_off()
>>       photo.put("#%02x%02x%02x" % (0,0,0), (x,y))
You can't expect a delay to happen during the mainloop() of the
program. To interrupt the mainloop(), use: parent.after(n,someCommand)
Where 'n' is some amount of milliseconds. Just have the parent widget
or the root frame call it.

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#97854

In article <mailman.66.1445391898.878.python-list@python.org>, 
illusiontechniques@gmail.com says...
 
[snip]

> If you want to pass arguments to a command called when a button is
> clicked, you have to use 'lambda' in tkinter.

Thanks. I just skimmed over lambda before now...

> You can't expect a delay to happen during the mainloop() of the
> program. To interrupt the mainloop(), use: parent.after(n,someCommand)
> Where 'n' is some amount of milliseconds. Just have the parent widget
> or the root frame call it.

When I read your post, I realized I'm doing 
a crude animation. After a bit of searching 
on 'python canvas animation', I found a 
reference to how it's done:

I made my 'root' Tk instance global, and 
call root.update_idletasks() after the 
.put

It works great! Now back to the lambdas 
(Ralph the Wonder Lambda, Earl J Lambda, 
Mike Q Lambda III, et al?).

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#97859

On 10/21/2015 1:50 AM, Randy Day wrote:

> When I read your post, I realized I'm doing
> a crude animation. After a bit of searching
> on 'python canvas animation', I found a
> reference to how it's done:
>
> I made my 'root' Tk instance global, and
> call root.update_idletasks() after the
> .put

I did not see the original post, but the alternative way to animate is 
to use root.after(milliseconds, callback, *args) at the end of callbacks 
to allow the event loop to process other events before re-calling the 
same or another callback.

-- 
Terry Jan Reedy

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#97863

In article <mailman.71.1445413916.878.python-list@python.org>, 
tjreedy@udel.edu says...

[snip]

> > I made my 'root' Tk instance global, and
> > call root.update_idletasks() after the
> > .put

> I did not see the original post, but the alternative way to animate is 
> to use root.after(milliseconds, callback, *args) at the end of callbacks 
> to allow the event loop to process other events before re-calling the 
> same or another callback.

I could see that being useful for creating
a steady frame rate in longer animations.
I'll put that one in my Python toolbox as well.


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