Item Data

Packet ID	Direction	Mojang Name	MCP Name
`0x83`	Clientbound	`ComplexItemDataPacket`	`Packet131MapData`

Used for sending pixel data for the map item.

Clientbound

Field	Type	Description
Item ID	Short	ID of the modified Item
Map ID	Short	ID of the map that should be displayed
Data Size	Byte	Size of the data array
Data	Byte Array	Array containing the data

The data that results from this has a format completely unique to it.

The first byte determines if the sent data is map graphics data (0) or map icon data (1).

If the sent data is map data, the next two Bytes are the X and Y offset of the updated map region.

After this follows the map data.

Each icon uses 3 bytes of data.

#	Data
0	Rotation (upper 4-bits), Icon Sprite (lower 4-bits)
1	X offset
2	Y offset

Valid icon rotation values range from 0 - 15 and maps to 0.0 - 360.0.

A map can, at most, have (256 - 1) / 3 = 85 icons.