Ruby Forum Ruby-Gnome 2 > pixbuf - memory leak?

Hello,

I am using gtk2 for image processing and the memory usage consistently
grows (memory never gets reclaimed).

The code is along the lines:

# pixell coordinates to memory address of the first byte)
def p2i(px, py, channels, rowstride)
  px * channels + py * rowstride
end

def process_image(pixbuf, output_dir)
  pixbuf.width.times do |x|
    pixbuf.height.times do |y|
      sample = pixbuf.pixels[p2i(x, y, pixbuf.n_channels,
pixbuf.rowstride), pixbuf.n_channels]
      # do something with the sample here
    end
  end
end

def process_images(input_dir, output_dir)
    image_paths = Dir.glob(input_dir + "/*.png").sort

    for ip in image_paths
        pixbuf = Gdk::Pixbuf.new(ip)
  process_image(pixbuf, output_dir)
    end

end

Am i supposed to call garbage collection by hand or the gtk2 is not
supposed to be used like this?

Vlad

Am Samstag, den 17.05.2008, 15:31 +0200 schrieb Vladimir Konrad:
> Hello,
> 
> I am using gtk2 for image processing and the memory usage consistently
> grows (memory never gets reclaimed).

[snip]
> 
> Am i supposed to call garbage collection by hand

yes, for now you have to start the GC on your own if you big amounts of
data very fast.

Cheers, detlef

>> Hello,
>> 
>> I am using gtk2 for image processing and the memory usage consistently
>> grows (memory never gets reclaimed).
> 
> [snip]
>> 
>> Am i supposed to call garbage collection by hand
> 
> yes, for now you have to start the GC on your own if you big amounts of
> data very fast.

Thanks for the pointer.

Well, to process one image takes minutes...

I have put the GC.start at the relevant place (in the cycle after 
process_imate() call) and will see what happens...

Vlad

Am Samstag, den 17.05.2008, 18:33 +0200 schrieb Vladimir Konrad:
> > data very fast.
> 
> Thanks for the pointer.
> 
> Well, to process one image takes minutes...
> 
Sorry, i've overlooked something in your example. Here

sample = pixbuf.pixels[p2i(x, y, pixbuf.n_channels,
pixbuf.rowstride), pixbuf.n_channels]

you create for every single pixle an array with all pixels from the
pixbuf. That must be horrible slow. Change your method as followed:

def process_image(pixbuf, output_dir)
  pixels = pixbuf.pixels
  pixbuf.width.times do |x|
    pixbuf.height.times do |y|
      sample = pixels[p2i(x, y, pixbuf.n_channels,
pixbuf.rowstride), pixbuf.n_channels]
      # do something with the sample here
    end
  end
end


Cheers, detlef

Am Samstag, den 17.05.2008, 19:14 +0200 schrieb Detlef Reichl:

Another speedup you'll get, if you precalculate some variables like
this:

  pixels = pixbuf.pixels
  w = pixbuf.width
  h = pixbuf.height

  h.times do |y|
    rs = y * pixbuf.rowstride
    ch = pixbuf.n_channels
    w.times do |x|
      sample = pixels[x * ch + rs]
    end
  end



Cheers, detlef

Detlef Reichl wrote:

> you create for every single pixle an array with all pixels from the
> pixbuf. That must be horrible slow. Change your method as followed:

(blushing for being stupid publicly ;-)

Thanks to all who replied,

I have re-done the method (create pixels array once per picture) - it 
works faster and also it looks that the memory usage is OK.

Vlad