An Atlas image is a picture file which contains several smaller images and a text file with coordinates of those tiles.
For example, if you have a 256x256 image called "tiles.png", which contains a 2 x 2 grid of smaller pictures (128 x 128 pixels), then you would have a 2nd file called "tiles subimages.txt" which contains;
0:0:0:128:128
1:128:0:128:128
2:0:128:128:128
3:128:128:128:128
Here, the first column is the name of the subimage, which can be any name but it is often easier to use numbers so they can be loaded with a loop.
The second and third columns contain the x and y coordinates of the top left corner of the sub image, the fourth and fifth contain the x and y size of that subimage.
In this case a neat grid of images which are the same size, though they do not need to be in a grid or even the same size
To use, load the main image as normal with something like;
mainImage = loadImage ( "tiles.png" )
the sub images can then be loaded, in this case using a simple loop, storing their pointers in an array;
dim spriteImage [ 3 ]
for i=0 to 3
spriteImage [ i ] = loadSubImage ( mainImage , str ( i ) )
next i
Now even though you have pointers to five images, only one (the main one) actually uses any memory, the other four simply refer to that main image.
All this is done internally within AppGameKit , you just treat them like any other image.
Just be careful if you plan to do texture manipulation, such as UV scrolling as Atlas files come with some limitations.
But as they used to say on "Mr Ben", that's another story
