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From someone who pushes pixels every day:
You almost certainly don't want a pixel-processing framework that
breaks things down to pixels!
Most interesting operations on images require a neighbourhood of
pixels, or even whole-image information. Furthermore, even for those
manipulations that don't, a function call per pixel is a huge amount
of overhead. Since you mention doing this as a framework, I can only
imagine that the compiler wouldn't even get to inline the per-pixel
function, making speedy execution impossible. With real-sized images
being in the greater than 2kx3k range these days, you're looking at
*a lot* of function calls.
Instead, I'd advise you look at a channel-based representation: break
up RGBA into 4 larger buffers and pass those to your
"doSomethingWithImage" function. The addressing requirements are
simple and it's easy to address sub-images (call the total width
"pitch", and pass that separately from your current "tile" width).
And the compiler will have a much easier time unrolling your loops!
Paul
On 2-Apr-07, at 1:29 AM, <[EMAIL PROTECTED]> wrote:
It is intended to be a general 'template' for operations on single
pixel, like, e.g., rotation in RGB-space. It should jump the pixels
and feed its RGB(A) values to the function doSomethingWithPixel().
I would like to (re)write some image manipulation functions, like
color balance, gamma, ...
from NetPBM, and from elsewhere, to native 9 code working on 9 images.
I suffer from being a self-made-man in computing, and of course,
from a lack of spare time, as everybody today. Although I did some
APE&native ports of my favourite programs, I love plan 9 so much
that I want to rewrite some of them in a clean way.
I have much to do with digital imaging, either at work, or as a
hobby. I must e3mphasize here that I dont like the paradigm of
'applications' -- user intensive programs, so I'd like to follow
the UNIX/Plan9 paradigm of well-tuned single-purpose programs
working together glued via a rc script, if I got it right.
Thus, any helping hand ismuch appreciated. Hopefully, one day I'll
do rm -fr /n/linux, as i did it with Windoze several years ago.
Back to the question: for the time being, the 'rgb.c' program,
after defining the 'do Something...() function to do nothing,
should write exactly the same image out, as was the one on the input.
Thanks for your care,
have a great day,
++pac.
-----Original Message-----
From: [EMAIL PROTECTED] on behalf of erik
quanstrom
Sent: Fri 3/30/2007 3:44 PM
To: [email protected]
Subject: Re: [9fans] code inspection needed/appreciated
could you please explain this code a bit futher. i'm not sure i
understand
what it's supposed to do and how it would be used.
- erik
Hello all!
I have put a simple code that is intended to manipulate individual
RGB pixels, on:
/n/sources/contrib/pac/sys/src/cmd/img/rgb.c
If anyone has time and is willing to help me, I would appreciate
inspecting the code and telling me your comments!!
Thank you,
have a great weekend,
<winmail.dat>
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