Map item format

Since Beta 1.6 craftable maps were added. They are placed in a data folder in the save folder. Each map have its own file with an incremental number and one file keeps track of the latest number added. This is limited to the size of a short(65,536). When Notch were adding them the first time he did not use NBT.

The structure tells that there will probably be an additional feature of maps with different zoom, size and probably maps for Nether.

Data folder structure
Each map starts with map_, have one unique number and ends with .dat. The file idcounts.dat contains the latest id for current map.

map_.dat Format
This file have a incremental number in it. The name for the map is in the name of the file, as the name is not in the file.

NBT Structure
The structure of the file is as follows:


 * TAG_Compound("data")
 * TAG_Byte("scale"): Probably how zoomed in the map is. Default 3
 * TAG_Byte("dimension"): Probably for mapping not only normal world, but Nether as well
 * TAG_Short("height"): Height of map. Default 128
 * TAG_Short("width"): Width of map. Default 128
 * TAG_Int("xCenter"): Center of map according to real world by X
 * TAG_Int("zCenter"): Center of map according to real world by Z
 * TAG_Byte_Array("colors"): Color id's

idcounts.dat Format
This file keeps track of the latest map added

NBT Structure
The structure of the file is as follows:


 * TAG_Short("map"): Current map id