From: Robert Klemme <shortcutter@...>
Date: 2009-12-08T01:23:53+09:00
Subject: Re: Reading Images

2009/12/7 Alexandro Kez <alexandro.mail@gmail.com>:
>
> Ok, here's the code. I'm just trying to load it and put on a quad. 500
> and 500 are the original width and height of pic.
>
>   name = GL.GenTextures(1);
>
>   data = File.open("grass.jpg", "rb") {|io| io.read}
>
>   GL.PixelStorei(GL::UNPACK_ALIGNMENT, 1);
>
>   GL.BindTexture(GL::TEXTURE_2D, name[0]);
>
>   GL.TexParameteri(GL::TEXTURE_2D, GL::TEXTURE_WRAP_S, GL::CLAMP);
>   GL.TexParameteri(GL::TEXTURE_2D, GL::TEXTURE_WRAP_T, GL::CLAMP);
>   GL.TexParameteri(GL::TEXTURE_2D, GL::TEXTURE_MAG_FILTER,GL::NEAREST);
>   GL.TexParameteri(GL::TEXTURE_2D, GL::TEXTURE_MIN_FILTER,GL::NEAREST);
>   GL.TexImage2D(GL::TEXTURE_2D, 0, GL::RGBA, 500,
>    500, 0, GL::RGBA, GL::UNSIGNED_BYTE,
>                data.unpack("C*"));
>
>
>    GL.BindTexture(GL::TEXTURE_2D,name[0]);
>    GL.Begin(GL::QUADS);
>    GL.TexCoord(0.0, 0.0); GL.Vertex(-20.0, 0.0, -20.0);
>    GL.TexCoord(0.0, 1.0); GL.Vertex(-20.0, 0.0, 20.0 );
>    GL.TexCoord(1.0, 1.0); GL.Vertex(20.0, 0.0, 20.0 );
>    GL.TexCoord(1.0, 0.0); GL.Vertex(20.0, 0.0, -20.0 );
>    GL.End();
>
>
>
> The error I get:
> Length of specified data doesn't correspond to format and type
> parameters passed. Calculated length: 1000000 (ArgumentError)
>
> As I think it may be due to the fact it contains more data, like width
> and height in itself and the datatypes, just don't get it. By the way,
> if I read it, it's still a string, why? Why do I have to pack/unpack?
> thanks to every respond

Do you have to unpack?  I don't know the GL API but I doubt it would
require to unpack the String.  Did you test what happens when you
unpack?  You get an Array full of ints.  That does not look like a
type that a low level graphics rendering library would use.  Methinks
GL would rather use a String (as the Ruby type for binary data).  What
do the docs say?

Kind regards

robert


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