Thanks to a contribution from Toshiba, X3DOM now supports compressed textures!
Although being slightly larger during transmission, compressed textures have the great advantage that they can be stored as-is on the GPU, thereby saving texture memory. This is especially useful in applications that use a lot of texture data, such as geospatial applications or games.
ImageTexture and ImageTextureAtlas now also accept dds files: if loading a texture as a jpeg/gif/png fails, X3DOM tries to load it as a compressed texture if the corresponding WebGL extension exists on the client platform. You can find a tech demo here.