From: Matthew Desmarais <desmarm@...>
Date: 2005-07-21T01:14:05+09:00
Subject: Re: Imlib2 to OpenGL textures

Hi Alex,

Have you tried something like this?

class Imlib2::Image
  def rgba_data
    self.data[1..3] << self.data[0]
  end
end

Hope that helps...

Matthew

AlexG wrote:

>Hi,
>
>I'm using Imlib2 to load textures for openGL. Imlib2's raw data output
>seems to be four unsigned bytes for each pixel in the order: ARGB
>(where A=alpha), whilst OpenGL expects RGBA. The code below adds a new
>method to Imlib2::Image to move the alpha byte to the end of each pixel
>(i.e. it turns 255 100 100 100 into 100 100 100 255) and seems to work
>OK. My question is: Is there a more elegant (and/or quicker) way to do
>this byte swapping? How do other people do this conversion?
>
>class Imlib2::Image
>  def rgba_data
>    new_data = ""
>    i = 0
>    a = ""
>    self.data.each_byte do |byte|
>      i += 1
>      if i % 3 == 0
>        new_data << a
>        a = byte
>      else
>        new_data << byte
>      end
>    end
>    new_data << a
>  end
>end
>
>Alex Gutteridge
>
>[1]: http://www.pablotron.org/software/imlib2-ruby/doc/
>
>
>
>  
>