[Caml-list] writing images with lablgl

[Caml-list] writing images with lablgl

[Damien]

Hi,

Is there an easy way to save a "labgl(ut) picture" to a file ?
Is there a way of doing it without displaying the picture ?

(I have got a list of polygons to render into a file)

Thanks,
damien


<http://www.ens-lyon.fr/~dpous/>

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Re: [Caml-list] writing images with lablgl

[Nickolay Kolchin-Semyonov]

On Wednesday 30 April 2003 12:29, Damien wrote:
> Hi,
>
> Is there an easy way to save a "labgl(ut) picture" to a file ?
> Is there a way of doing it without displaying the picture ?
>
> (I have got a list of polygons to render into a file)
>

You can use glReadPixels and glReadBuffer save BACK image from OpenGL to 
memory. Converting pixel data to image format is your task. I'am not sure 
that this functions are supported by lablgl. If not, you can use camlgl 
(http://www.sf.net/projects/camlgl)

Nickolay

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Re: [Caml-list] writing images with lablgl

[Damien]

> You can use glReadPixels and glReadBuffer save BACK image from OpenGL
> to memory. Converting pixel data to image format is your task. 

I have done it for PPM : 

  let save_ppm s = 
    let o = open_out s in
    let w = Glut.get Glut.WINDOW_WIDTH  in
    let h = Glut.get Glut.WINDOW_HEIGHT in
      Printf.fprintf o "P6\n%d %d\n%d\n" w h 255;
      let w3 = 3*w in
      let r = GlPix.to_raw (GlPix.read 0 0 w (3*h) `rgb `ubyte) in
	for j = h-1 downto 0 do
	  output_string o (Raw.gets_string r (w3*j) w3)
	done;
	close_out o

why not to include this kind of boring function into lablgl(ut) ?
(or at least somewhere in the examples...)

damien

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Re: [Caml-list] writing images with lablgl

[Nickolay Kolchin-Semyonov]

On Thursday 01 May 2003 12:53, Damien wrote:
> > You can use glReadPixels and glReadBuffer save BACK image from OpenGL
> > to memory. Converting pixel data to image format is your task.

Just for completness, PPM saving function for camlgl:

   let dump_screen name =
        try
            let f = open_out_bin name in
            let (x1,y1,x2,y2) =
                let a = Hgl.ba_int 4 in
                glGetIntegerv cgl_viewport a;
                a.{0},a.{1},a.{2},a.{3}
            in
            let w = x2 - x1 and h = y2 - y1 in
            let b = Hgl.ba_byte (w * h * 3) in
            glReadPixels x1 y1 x2 y2 cgl_rgb cgl_unsigned_byte b;
            Printf.fprintf f "P6\n%i %i\n255\n" w h; flush f;
            for y = 1 to h do
                let sy = (h-y)*w*3 in
                for x = 0 to w*3 - 1 do
                    output_byte f b.{sy+x}
                done
            done;
            close_out f
        with _ -> Printf.printf "dumping failed\n"; flush stdout

Nickolay

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