You can cut a bmp into Tiles without even touching the bmp... this is code straight from my tile editor
`This will be the BMP you want to cut up
load bitmap "TileSet.Bmp"
`This is how many tiles your bmp contains
`A 640 x 480 bmp will consist of 300 tiles
NumberOfTiles = 300
`640 divided by 32 is equal to 20 so there are
`20 32x32 tiles per Xrow (Horizontal Row)
Xrow = 20
`The For loops which cuts the bmp into 300 32x32 square tiles.
for a = 1 to NumberOfTiles
get image TileCount+1,TileX*32,TileY*32,(TileX*32)+32,(TileY*32)+32
inc TileCount
inc TileX
if TileX=XRow
TileX=0
inc TileY
endif
next a
My Tile Editor can be found at this link and if you download it, it will come with all the Source.
http://forum.thegamecreators.com/?m=forum_view&t=51923&b=8

http://www.angelfire.com/games5/db_games/