Sprite bank file

(Up to File formats)

A sprite bank file is used to store multiple Sprite file in a very efficient manner. All sprites in a BNK file are compressed using Team17 compression and they all share one palette.

BNK files are used both by Worms World Party and Worms World Party Aqua in their gfx.dir and water.dir files.

File Format

Size	Type	Description
4	int32	Signature. The magic number used to identify the BNK file. Hex: 0x424E4B1A, ASCII: "BNK\1A"
4	int32	File Length The total length of the file.
2	int16	Palette Count The number of palette entries, excluding back color.
3 * i	byte[,]	Palette The palette used for all frames in the file. Each palette entry is 3 bytes long, stored in BGR format. (sized as new byte[PaletteCount, 3])
0 to 3	byte[]	Padding Padding is added to put the data in 4 byte position. (pos + 2) % 4
4	int32	Sprite Count The total number of sprites stored in the file.
12 * i	Sprite[]	Sprite Info The data explaining how to get and display the sprite animations. (sized as new Sprite[SpriteCount])
4	int32	Frame Count The total number of frames stored in the file.
12 * i	Frame[]	Frame Info The data explaining how to get and display the individual frames of a sprite animation. (sized as new Frame[FrameCount])
4	int32	Stream Count The total number of compressed data streams stored in the file.
12 * i	Stream[]	Stream Info The data explaining how to get and decompress the image data streams. (sized as new Stream[StreamCount]])
var	Stream[]	Stream Data The compressed image data streams.

The Sprite Struct

Size	Type	Description
2	int16	Flags The play back settings.
2	int16	Width The cell width of the animation.
2	int16	Height The cell height of the animation.
2	int16	Frame Start The starting frame number for the animation.
2	int16	Frame Count The total number of frames for the animation.
1	byte	Unknown Unknown, but important.
1	byte	Frame Rate The tick delay between frames.

The Frame Struct

Size	Type	Description
2	int16	Stream The stream number that the frame image data is stored in.
2	int16	Data Position The starting position of the frame image data in the decompressed stream.
2	int16	Left Offset The left offset of the image data relative to the sprite cell.
2	int16	Up Offset The up offset of the image data relative to the sprite cell.
2	int16	Right Offset The right offset of the image data relative to the sprite cell.
2	int16	Down Offset The down offset of the image data relative to the sprite cell.

The Stream Struct

Size	Type	Description
4	int32	Compressed Position The starting position of the compressed data stream.
4	int32	Decompressed Length The total length of the decompressed data stream.
4	int32	Unknown Unknown, most likely useless.
var	byte[]	Compressed Image Data The compressed data stream's binary data. (see Decompression Routine in Team17 compression)