Date: Fri, 20 Aug 2004 14:00:44 +0200 (CEST)
Message-Id: <20040820.140044.59461890.andrieu at ijm.jussieu.fr>
To: seguso.forever at tin.it
Cc: lablgtk at kaba.or.jp
Subject: Re: Loading a texture from file and applying it?
From: Olivier Andrieu <andrieu at ijm.jussieu.fr>
In-Reply-To: <200408191934.19330.seguso.forever at tin.it>
References: <200408181845.37672.seguso.forever at tin.it>
	<20040819.120933.41629782.oandrieu@nerim.net>
	<200408191934.19330.seguso.forever@tin.it>
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 Maurizio Colucci [Thu, 19 Aug 2004]:
 > On Thursday 19 August 2004 12:09, Olivier Andrieu wrote:
 > >  Maurizio Colucci [Wed, 18 Aug 2004]:
 > >  > Hello again,
 > >  >
 > >  > In lablgl + lablgtk, I need to load a texture from file and apply it to
 > >  > a triangle.
 > >  >
 > >  > More precisely: GlTex.image2d wants a byte array as a GlPix. I need
 > >  > to know how to create a GlPix from a png file (or similar).
 > >
 > > You can use GdkPixbuf: it will load the png file and convert it
 > > into a "pixel buffer" structure. You then need to convert this
 > > into a Raw array.
 > >
 > > The easiest way is to do this:
 > > ,----
 > > | let raw_of_pixbuf pb kind =
 > > |   Raw.of_string (Gpointer.string_of_region (GdkPixbuf.get_pixels pb))
 > > | ~kind
 > > `----
 > >
 > 
 > Thank you very much Olivier. I was looking at ocamlimages, so your hint was 
 > very useful. I still have some doubt though.
 > 
 > This is the code I have managed to write so far:
 > 
 >   let pb = GdkPixbuf.from_file "avatar1giu.bmp" in
 >   let wt = GdkPixbuf.get_width pb in
 >   let ht = GdkPixbuf.get_height pb in
 >   let wt2 = round wt in
 >   let ht2 = round ht in
 >   let pb_sc = GdkPixbuf.create ~width:wt2 ~height:ht2 
 >     ~bits:8 (* 8 bits per sample * 4 samples=32 bits *)
 >     ~has_alpha:true () in
 >   GdkPixbuf.scale ~dest:pb_sc ~width:wt2 ~height:ht2 pb;
 >   let raw_of_pixbuf pb kind =
 >     Raw.of_string (Gpointer.string_of_region
 > 		     (GdkPixbuf.get_pixels pb)) ~kind in
 >   let raw = raw_of_pixbuf pb_sc  ??? in
 > 
 > 
 > 1. As you can see, I don't know what to pass as kind. Could you please tell 
 > me?

`ubyte should be ok I guess; it doesn't really matter unless you want
to read/write the pixels in the raw array.

 > 3. What do I do with this raw array? At the end, I need a GlPix.t to pass to 
 > GlTex.image_2d. Must I use GlPix.of_raw?

most probably

 > 4. Before calling GlTex.image_2d, I have to set the alpha value of
 > my image manually, pixel per pixel (to set up color key). What can
 > I use to read and write the red, green, blue and alpha values?

If what you have to do is make a certain color transparent, that's
easy to do with the gdkpixbuf. GdkPixbuf.add_alpha has an optional
argument that specify a color to be made transparent. 

-- 
   Olivier