(OpenGL) texture from matrix

[brixton]

Hello,

I've got the following code that creates a texture from a .RAW file:

GLuint MyGLCanvas::LoadTextureRAW( const char * filename, int wrap )
{
    GLuint texture;
    int width, height;
    BYTE * data;
    FILE * file;
 
    // open texture data
    file = fopen( filename, "rb" );
    if ( file == NULL ) return 0;
 
    // allocate buffer
    width = 64;
    height = 64;
    data = (BYTE*)malloc( width * height * 3 );
 
    // read texture data
    fread( data, width * height * 3, 1, file );
    fclose( file );
 
    // allocate a texture name
    glGenTextures( 1, &texture );
 
    // select our current texture
    glBindTexture( GL_TEXTURE_2D, texture );
 
    // select modulate to mix texture with color for shading
    glTexEnvf( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE );
 
    // when texture area is small, bilinear filter the closest mipmap
    glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
                     GL_LINEAR_MIPMAP_NEAREST );
    // when texture area is large, bilinear filter the first mipmap
    glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
 
    // if wrap is true, the texture wraps over at the edges (repeat)
    //       ... false, the texture ends at the edges (clamp)
    glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S,
                     wrap ? GL_REPEAT : GL_CLAMP );
    glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T,
                     wrap ? GL_REPEAT : GL_CLAMP );
 
    // build our texture mipmaps
    gluBuild2DMipmaps( GL_TEXTURE_2D, 3, width, height,
                       GL_RGB, GL_UNSIGNED_BYTE, data );
 
    // free buffer
    free( data );
 
    return texture;
}

That works fine. However, I want to generate a texture from a matrix of double values (using a matrix library) instead. It's stored indexed like Matrix(x,y).

So, the question is: how do I modify this to get my matrix values into the "data" array? Can "data" be of double type?

Apologies if it's a silly question, but I'm new to all things OpenGL.

Thanks.