[Plib-users] Texture with transparency

[Michael W. <michael.wessels@z.zgs.de>]

Hi all,

I am using the following code to load a bmp-image with ssgTexture.

---------------------------------------------------------------------------

 // Load of a BMP-Image with the Library PLIB
    GLuint FDS_Load_Image_BMP(char *filename,GLuint tex_obj, bool
transparent)
 {
 unsigned int i;
 int t_r,t_g,t_b,t_a;
 IMAGE_BMP bmp ;
    size_t npixels;
 GLuint tex_handle, map_level ;
    tex_list = new ssgTexture ( filename ) ;
    tex_handle = tex_list->getHandle();
 if(transparent)
 {
  map_level = 7 ;
 glBindTexture(GL_TEXTURE_2D,tex_handle);
 glGetTexLevelParameteriv(GL_TEXTURE_2D,map_level,GL_TEXTURE_WIDTH,&bmp.width);

 glGetTexLevelParameteriv(GL_TEXTURE_2D,map_level,GL_TEXTURE_HEIGHT,&bmp.height);

 glGetTexLevelParameteriv(GL_TEXTURE_2D,map_level,GL_TEXTURE_COMPONENTS,&bmp.components);

 npixels = bmp.width * bmp.height ;
    bmp.raster = (uint32*) _TIFFmalloc(npixels * sizeof (uint32));
 glGetTexImage(GL_TEXTURE_2D,map_level,GL_RGBA,GL_UNSIGNED_BYTE,&bmp.raster);

    for (i = 0; i < npixels; i++)
    {
      unsigned char *cp =  (unsigned char *) &bmp.raster[i];

      t_r = cp[0];
      t_g = cp[1];
      t_b = cp[2];
      t_a = cp[3];
   if((t_r==0)&&(t_g==0)&&(t_b==0))
   {
    cp[3]=0;
   } else
   {
    cp[3]=255 ;
   }
   }
 glBindTexture(GL_TEXTURE_2D,tex_obj);
   glTexImage2D(GL_TEXTURE_2D,0,4,bmp.width,bmp.height,
               0,GL_RGBA,GL_UNSIGNED_BYTE,bmp.raster);
   tex_handle = tex_obj ;
 }
 return tex_handle ;
 }
-----------------------------------------------------------------------------------

The code works well, if a dont use transparent = false .
I know that the images are put in SSG to a texture with using mipmaps.
My understandig is, that I can get the image-raster using map_level = 0
 glGetTexImage(GL_TEXTURE_2D,map_level,GL_RGB,GL_UNSIGNED_BYTE,&bmp.raster);

. In this case the texture is completley transparent. The original
bitmap has dimensions of 128*256. With map_level 6 I get a small stripe
with two different colors in width direction.

Has anybody an idea what I am making wrong ?

With regards

Michael