Bug already reported.
http://www.blitzbasic.com/Community/posts.php?topic=71621
Some people think it's not a bug, but I think it is. Textures do have alpha channels, as well as 32bit graphics modes. But Blitz3D doesn't copy the whole 32bit, only 24 bit (RGB color values). So we are out of luck for this one. If you build your texture in memory as an image, you can't define alpha values and then copy that back to the texture buffer.
http://www.blitzbasic.com/Community/posts.php?topic=71621
Some people think it's not a bug, but I think it is. Textures do have alpha channels, as well as 32bit graphics modes. But Blitz3D doesn't copy the whole 32bit, only 24 bit (RGB color values). So we are out of luck for this one. If you build your texture in memory as an image, you can't define alpha values and then copy that back to the texture buffer.