in all of the bitblting tutorials ive read, it make a sprite with you need the original bitmap and another one which acts as a mask, having the black parts = original colours and white parts = transparent....

What ive been wondering is, where does the mask come from?! Do you have to make it yourself?? Say, in a graphics program, paint all the sections u want to be transparent to white and all the parts you want kept to black??

tutorials never answers this basic question..