For creating image atlases I use the excellent TexturePacker
https://www.codeandweb.com/texturepacker - It has support for AppGameKit but just needs the image coordinates file changed to <filename> subimages.txt
So lets say we create an image atlas called blobSheet.png with blob1.png, blob2.png and blob3.png ( simple 64 x 64 circles in red, green and blue )
Using TexturePacker as our example atlas creator we would end up with an image like :
Our corresponding sub images file would have the following info :
blob1.png:2:2:64:64
blob2.png:2:68:64:64
blob3.png:2:134:64:64
It is ordered in image name, x, y, width, height on the atlas image.
Now our code to use this in AppGameKit would be as simple as :
atlasImage1 = LoadImage( "blobSheet.png" )
atlasBlobRed = LoadSubImage( atlasImage1, "blob1.png" )
atlasBlobGreen = LoadSubImage( atlasImage1, "blob2.png" )
atlasBlobBlue = LoadSubImage( atlasImage1, "blob3.png" )
blobRed = CreateSprite( atlasBlobRed )
blobGreen = CreateSprite( atlasBlobGreen )
blobBlue = CreateSprite( atlasBlobBlue )
Then the usual sprite commands apply as per normal. Hope the above makes sense on how to use the atlas commands. If an example project would help then let me know and I'll whip up one for you.