Hi Guillermo,
Glad you have progress! A quick change that will compute a bit less is to
change:
$image->where($sub_image > 0) .= $sub_image->where($sub_image > 0);
to:
my $inds = $sub_image > 0;
$image->where($inds) .= $sub_image->where($inds);
The algorithm you're using looks like it takes, for each pixel channel, the
last (highest-n) non-zero pixel channel value. There isn't a "first non-zero"
(which you could use with a slice("-1:0")) operation that I know of, but if
there were, it would operate over the whole image-stack in one go, which would
probably be optimally quick, especially since it would shortcut. Also with the
miracle of auto-pthreading and broadcasting, it could use POSIX threads.
Any volunteers to write a "firstnonzeroover" xform for Ufunc?
Best regards,
Ed
________________________________
From: Guillermo P. Ortiz <[email protected]>
Sent: 25 October 2024 5:29 PM
To: Ed . <[email protected]>
Cc: David Mertens <[email protected]>; [email protected]
<[email protected]>; [email protected]
<[email protected]>
Subject: Re: [Pdl-devel] project ordered sequence image
Thanks to Ingo, David, Ed,
After some minor modification to the David help, and using:
use PDL::NiceSlice;
my $image = $imn(,,,(0));
for my $layer (1 .. $imn->dim(3)-1) {
my $sub_image = $imn(,,,($layer));
$image->where($sub_image > 0) .= $sub_image->where($sub_image > 0);
}
works fine to solve my problem, but yes it is some slow thinking in hundreds of
these
operations. Nevertheless, it does not impact the overall computation cost.
The change I made is $image->dim(3) => $imn->dim(3)-1, because $image is
(3,x,y) and the number of layer is
in $imn->dim(3)
Regards
El vie, 25 oct 2024 a las 9:42, Ed .
(<[email protected]<mailto:[email protected]>>) escribió:
A thing I didn't think of before: to add to David's thought, you might consider
adding a fourth value to make your images RGBA, where the A is "alpha", i.e.
opacity. Then you would only add each pixel (or channel value) to the final
image where its numerical value * the alpha value was >0 (or, if you're doing
addition or "or"-ing, just add/or the value * the alpha, which if 0 does
nothing).
Best regards,
Ed
________________________________
From: David Mertens <[email protected]<mailto:[email protected]>>
Sent: 25 October 2024 11:10 AM
To: Ed . <[email protected]<mailto:[email protected]>>
Cc: Guillermo P. Ortiz <[email protected]<mailto:[email protected]>>;
[email protected]<mailto:[email protected]>
<[email protected]<mailto:[email protected]>>;
[email protected]<mailto:[email protected]>
<[email protected]<mailto:[email protected]>>
Subject: Re: [Pdl-devel] project ordered sequence image
Hello Guillermo,
You said something interesting. You discussed a sub-image with "a red circle"
and another with "a blue rectangle". But what you have are full images: an
image with a red circle is an image with a red circle and a black background.
It sounds like you want to treat that background color as transparent, then
"layer" the images by overwriting the non-transparent pixels.
If I had to do this myself, I can only think of a way to do this using a Perl
loop. If you find that this loop is too slow, then think of ways to rewrite
using a PDL expression, but only if you actually deem it to be too slow. It
would go something like this:
use PDL::NiceSlice;
my $image = $imn(,,,(0));
for my $layer (1 .. $image->dim(3)) {
my $sub_image = $imn(,,,($layer));
$image->where($sub_image > 0) .= $sub_image->where($sub_image > 0);
}
This isn't perfect: if you have a pixel in your sub-image that is pure red,
it'll copy the red channel to the final image, but not the green or blue.
That's as much as I can put into it for now, thouogh, and hopefully it's enough
to get you started.
David
On Thu, Oct 24, 2024 at 3:30 PM Ed .
<[email protected]<mailto:[email protected]>> wrote:
Hi Guillermo,
That will depend on how you want to combine each pixel. If you can deal
independently with each R/G/B value, then to just add the values together,
you'd do:
$im = $imn->mv(-1,0)->sumover;
Otherwise you'll have to spell out a bit more what you mean by sorting. Another
operation that might be useful is "borover" (bitwise or, on each R/G/B value
along the sequence of images).
Best regards,
Ed
________________________________
From: Guillermo P. Ortiz <[email protected]<mailto:[email protected]>>
Sent: 24 October 2024 4:52 PM
To: Ed . <[email protected]<mailto:[email protected]>>
Cc: [email protected]<mailto:[email protected]>
<[email protected]<mailto:[email protected]>>;
[email protected]<mailto:[email protected]>
<[email protected]<mailto:[email protected]>>
Subject: Re: [Pdl-devel] project ordered sequence image
Hello again, thanks to Ed for show me a typo error
in my example. Where I wrote
$im=$imn->reduce('op',2);
it must say
$im=$imn->reduce('op',3);
But, the question remain in how to do an 'op' that
result in a sorted overlapping between all the sub images
In other words. Suppose you have n=0 sub image with
a red circle and in n=1 a sub image with a blue rectangle.
Some pixeles of both images are in common.
Then, what I want is to get a composed image that shows
the red circle overlapping the blue rectangle. The same
idea for many subimages with sorted overlapping.
Regards,
El jue, 24 oct 2024 a las 9:57, Guillermo P. Ortiz
(<[email protected]<mailto:[email protected]>>) escribió:
Hello Ed,
thanks for your reply.
That I trying to mean with 'reduce' is some of
projection operation (op) like in PDL::Reduce module
that performs "(op)over" to reduce to N-1
dimension after some operation over the set of
(3,x,y, n) to (3,x,y) rgb images. I mean
a composed rgb image from a set of (layer) n rgb images.
For example:
$imn-> info : pdl D [3,nx,ny,n]
$im=$imn->reduce('op',2);
$im-> info : pdl D [3,nx,ny]
Then, maybe I need to introduce some "sort"
operation in order that when I reduce to one
composed $im image each layer in $imn overlap
the following layer. But, I did not realize how to do that
using some pdl trick.
Thanks a lot for your help
Regards
El jue, 24 oct 2024 a las 9:12, Ed .
(<[email protected]<mailto:[email protected]>>) escribió:
Hi Guillermo,
I believe the situation you're describing is you have effectively a series of
(3,x,y) images. You mention "reducing", but you haven't said what you mean by
that - would it turn that series of images into one image?
wpic is intended to write out a single image, so an ndarray with multiple
images won't work with that. To write out a series of images as a movie you
could use wmpeg, or just to store the data you could use
https://metacpan.org/pod/PDL::IO::FastRaw and specifically writefraw. Otherwise
to write each image in its own file you could use something like:
$_->wpic(sprintf "img%03d.png", $count++) for $pdl->dog;
Does that help?
Best regards,
Ed
________________________________
From: Guillermo P. Ortiz <[email protected]<mailto:[email protected]>>
Sent: 23 October 2024 4:42 PM
To: [email protected]<mailto:[email protected]>
<[email protected]<mailto:[email protected]>>;
[email protected]<mailto:[email protected]>
<[email protected]<mailto:[email protected]>>
Subject: [Pdl-devel] project ordered sequence image
Hello everyone,
I have created a pdl with structure (3,size_x,size_y,np)
in order to manage different layer features to compose an rgb
image.
The idea that I can not connect yet is how to "reduce" over dim 3
to project to 3 X s_x X s_y rgb image in ordered fashion sequence. For example,
suppose that for np=0, 1 and 2, in the resulting image is only view of 2 that
is allowed by 1 and 0 layers, in that order.
I am trying to use wpic command from PDL::IO::Pic module
to convert via for example pnmtopng using options for it.
There are hashes like {FLAGS => options} used for options
{CONVERTER => 'pnmtopng'} indicating which conversor to use.
But is seems to be intended of rgb 3(4) X s_x X s_y
Thanks for your attention in advance
Regards
--
Dr. Guillermo P. Ortiz
Electromagnetismo Aplicado
Dto. Física, Facultad de Ciencias Exactas
Universidad Nacional del Nordeste
Avda Libertad 5460, Campus UNNE.
W3404AAS Corrientes, Argentina.
(+54) 379-4424678 interno 4613
gortiz at unne edu ar
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