Blitz can load Images even if their Extension is wrong. so when a JPG is named BMP Blitz will nonetheless load it correctly. I use this feature to optimize the Project size before I release things. I pick the huge BMPs and save them as reasonably compressed JPGs, rename them to BMPs. With a lossy compression quality of 10 I usually have pretty small filesizes and almost no visual loss. especially for 512*512 Textures which are mippapped anyway (eg. on Characters) this makes sense. But you should first compare the filesize of a zipped BMP, sometimes this is even smaller than the JPG!
I agree: never ever use JPG for masks, and avoid it for Alpha-transparency. 32Bit TGAs cannot be replaced by JPGs anyway...
I agree: never ever use JPG for masks, and avoid it for Alpha-transparency. 32Bit TGAs cannot be replaced by JPGs anyway...