OpenGl Texture

OpenGl Texture

Post by Tersiu » Fri, 27 Jun 2003 02:21:35

In the examples dir of c++ builder there is a example under the dir
In this example textures are loaded by using the TBitmap component.
Here folows that code:

     bitmap = new Graphics::TBitmap;
     GLubyte bits[64][64][4];
     for(int i = 0; i < 64; i++)
        for(int j = 0; j < 64; j++)
             bits[i][j][0]= (GLbyte)GetRValue(bitmap->Canvas->Pixels[i][j]);
             bits[i][j][1]= (GLbyte)GetGValue(bitmap->Canvas->Pixels[i][j]);
             bits[i][j][2]= (GLbyte)GetBValue(bitmap->Canvas->Pixels[i][j]);
             bits[i][j][3]= (GLbyte)255;

     glGenTextures(1, &texture1);

     glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 64, 64, 0, GL_RGBA,                

In this example they allready know the height and width.
How would one load a texture with an unknown height and width?
Would one use dynamic arrays?
Could you please provide some code.
Thanks in advance.


OpenGl Texture

Post by Scott Heima » Fri, 27 Jun 2003 07:55:49

This is untested, uncompiled code written on the fly - but it should give
you the idea...

      bitmap = new Graphics::TBitmap;
      unsigned char *bits = new unsigned
    unsigned char *p = bits;
    for ( unsigned int i = 0; i < bitmap->Height; i++ )
        for ( unsigned int j = 0; j < bitmap->Width; j++ )
            p[0] = (GLbyte)GetRValue(bitmap->Canvas->Pixels[i][j]);
            p[1] = (GLbyte)GetGValue(bitmap->Canvas->Pixels[i][j]);
            p[2] = (GLbyte)GetBValue(bitmap->Canvas->Pixels[i][j]);
            p[3] = (unsigned char)255;
            p += 4;

      glGenTextures(1, &texture1);

      glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, bitmap->Height, bitmap->Width,

    delete [] bits;

There are other solutions as well.  My BMGLib will read several image
formats and convert them to bit arrays, which you can easily convert to
OpenGL textures.  You can download the project from my web site.  Look at
the 'texture' example in the Borland folder for an example.

(a valid e-mail address can be found on my home page)


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