I upload a 2D texture using :
GL_COMPRESSED_RGB_ARB as internal format and
GL_RGBA as format because my pixels (not compressed) are store on 4 bytes but I only use 3 components. So I don't care about alpha value. Nevertheless the rasterisation use the alpha component of the texture even if I not use the GL_COMPRESSED_RGBA_ARB ! Thus I must to set to 255 the alpha value (If I set 0 the texture appear black).
Any idea ?
NB : PixelStorage = 4