ST7735 display and picture and pictures

well i do not understand wich format can be used to directly loadImage from storage as in exemple!
is it a bmp file in 1bit? or a what?
how to put img file in the storage area of the espruino?
am i wrong, it only works with a sd card module?

i have to admit, i'm a beat confuse. sorry

g.drawImage(require("Storage").read("myi­mage.img"), 10, 10);