this simple line
local pack = TexturePack.new({'bird_black_01.png', 'bird_black_02.png'})
The reason why I try this is I wonder if I can get the effect of some pack algorithm like maxrects.
I think if we can pass a parameter for maxwidth or maxheight for the outline rectangle, we can put any number of image with any size on the screen in an area of size such as ? x 960, ? is increased by the image numbers.