Re: [Mesa3d-users] Capture Window pixel values using glReadPixels

[Srimal J. <sr...@gm...>]

Thanks a lot tom

Your right .

I've changed everything to C style and , removed the iostream.h and
included stdio.h

and it works now.

Regs

Srimal.

On Mon, Jul 27, 2009 at 11:02 AM, tom fogal<tf...@al...> wrote:
> Srimal Jayawardena <sr...@gm...> writes:
>>         GLvoid* data;
>>         data =3D (GLvoid *) malloc (1024*768);
>>         glReadPixels (0,0,1024,768,GL_RED, GL_UNSIGNED_BYTE, data);
>>         for(int i=3D0; i<1024*768; i++)
>>         cout << data[i];
>>         free(data);
>>
>> But it gives this error:
>>
>> $ make
>> g++ -Wall -o render main.cpp -lglut
>> main.cpp: In function =E2=80=98void drawScene()=E2=80=99:
>> main.cpp:154: error: pointer of type =E2=80=98void *=E2=80=99 used in arith=
>> metic
>> main.cpp:154: error: =E2=80=98GLvoid*=E2=80=99 is not a pointer-to-object t=
>> ype
>> make: *** [render] Error 1
>>
>> Am I missing something here?
>
> Yep.  In short, your types are wrong.  You can't have a void object, so
> you can't directly dereference a void pointer.  Try a GLubyte instead.
>
> That said, you might want to read up on C.  I suggest the white book:
>
>  http://cm.bell-labs.com/cm/cs/cbook/
>
> Though your `cout' implies you actually want to write C++, contrary to
> malloc/free.  Stroustrup's book is the classic text here:
>
>  http://www.research.att.com/~bs/3rd.html
>
>> Is there a better way to do this?
>
> Somewhere in the Mesa demos (IIRC) there's some code for reading the
> current image buffer into a ppm file.  If not there, some simple
> googling should bring up code to do this.
>
> -tom
>



-- 
~
Srimal Jayawardena
BSc (Engineering), BIT, MIET
PhD Student, Australian National University.

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