get(frame) gets slice of index frame - offset if unsure leave at 0
scale mode for slices
texture slices
texture atlas base texture (required in constructor)
calculated from cols/rows or passed in constructor
calculated from cols/rows or passed in constructor
how many pixels not put to slice from each side of frame
height read from texture
width read from texture
get lazy cached slice on index
Protectedloadused internally in get(frame) to load the slice first time
Protectedpreload
used internally to preload cached slices
for slicing textures into tileset