Re: [Foxgui-users]converting a JPEG file to an OpenGL texture map

[Jeroen v. d. Z. <jv...@cf...>]

On Tuesday 11 December 2001 09:36, you wrote:
> > > > Typical steps would be:
> > > > FXuchar *data;
> > > > FXint    width,height,qual;
> > > > FXColor  trans;
> > > > FXFileStream store;
> > > >
> > > > store.open(filename,FXStreamLoad);
> > > > fxloadJPG(store,data,trans,width,height,qual);
> > > > store.close();
> > > >
> > > > Note we have blatantly ignored errors; production code would test for
> > > > various errors, of course.
> > > >
> > > > Then, pass to OpenGL:
> > > >
> > > >     glPixelStorei(GL_UNPACK_ALIGNMENT,1);
> > > >     glGenTextures(1, &texname);
> > > >     glBindTexture(GL_TEXTURE_2D,texname);
> > > >     glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_REPEAT);
> > > >     glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_REPEAT);
> > > >     glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
> > > >     glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
> > > >
> > > > glTexImage2D(GL_TEXTURE_2D,0,GL_RGB,width,height,0,GL_RGB,GL_UNSIGNED
> > > >_BYT E,data);
> > >
> > > 
> > > It would seem as there is a problem with the above example.
> > > That is, where is the data stored?  All we have is a pointer
> > > to the data.  When we call FXFileStream.close() does the data
> > > persist?  Has the FXFileStream object allocated the appropriate
> > > room?  Or do we need to save the data before calling close()
> > > e.g. using fxSaveJPG()?
> > >
> > > -cheers, bob
> >
> > fxloadJPG allocates the array; it must be freed using FXFREE(&data).
> >
> > Sorry, I should have mentioned that.
> >
> >         - Jeroen
>
> 
> Thank you for your help thus far Jeroen.  It seems to be working
> now.  Ok, now i would like to store the JPEG image as part of
> the binary file.  i have already used reswrap to save the file
> directly into the executable. e.g. i have this in my header file:
>
> /* Generated by reswrap from file water32x32.jpg */
> const unsigned char m_Water32x32[]={
>
> 0xff,0xd8,0xff,0xe0,0x00,0x10,0x4a,0x46,0x49,0x46,0x00,0x01,0x01,0x00,0x00,
>0x01, ...
>
> Now, what are the steps to take to extract the RGB data.
> If i understand correctly, i first load this data into
> a FOXFileStream object, and then extract the RGB data.
> Is it the same 3 steps (open, load, and close) except
> instead of the filename i pass the array name?
>
> -cheers, bob

Use FXMemoryStream.

    FXMemoryStream ms;
    FXuchar *data;
    FXint    width,height,qual;
    FXColor  trans;
    ms.open(m_Water32x32,FXStreamLoad);
    fxloadJPG(ms,data,trans,width,height,qual);
    ms.close();


Should do the trick. Note works exactly the same as FXFileStream, i.e.
all the I/O working on FXStream's has no idea its coming from file or
memory data arrays.


Regards,


		Jeroen

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