From: "ara.t.howard" <ara.t.howard@...>
Date: 2008-06-16T13:52:15+09:00
Subject: Re: Binary string packing/unpacking issues


On Jun 14, 2008, at 4:53 AM, Lucas L. wrote:

> Hi,
> I have a packed string of raw binary pixel data that I want to
> manipulate. However, I'm facing a few problems.
> Firstly, the only way I've managed to unpack the data so far is with
> "pixels.unpack('b*')". It works great, but comes out in one massive
> string.
> Is there a way to:
> a)put this into an array with 8 bits in each element, eg. ['00000000',
> '01010101'...]
> b)unpack small sections of a few bites
> The other problem is that I don't know of an efficient way to  
> manipulate
> this data without having to unpack\pack massive strings each time.
>
> Are there any solutions to these?

use narray

a rather complicated example

   http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/155483

the basic starting point is

   width = 800
   height = 600

   na = NArray.to_na raw_pixel_data, NArray::BYTE, width, height

then to, for example, increase every pixel value by 1

   na += 1

see

   http://narray.rubyforge.org/SPEC.en

for more.

   gem install narray

too, of course.


regards.

a @ http://codeforpeople.com/
--
we can deny everything, except that we have the possibility of being  
better. simply reflect on that.
h.h. the 14th dalai lama