Minecraft: Custom symbols on maps?

Question

While browsing the Minecraft Wiki, I've stumbled upon a very interesting feature: it states (specifically here) that it is possible to add custom symbols (called "decorations") to maps - this looks very, very promising, especially for map-making, but lacks so many important details! What exactly the format of the type field? Do x and y fields relate to global (per-world) or local (per-map) coordinates? And if the latter, then what are their limits? This raises so many questions, and, obviously, it also lacks any examples...

I've tried to google it, but in vain: results are mostly about fancy map decorations, furniture and the staff. Could someone please explain this topic or link to someplace where it is already explained?

Answer 1

The available symbols (which type changes between) can be found in textures/map/map_icons.png:

1.10-                          16w39a+

type is an integer ranging from 0 (white arrow marker) to 6 (white circle) in 1.10, or to 9 (ocean monument) as of 16w39a.

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x and z are world coordinates, showing decorations that have absolute x and z values being within a certain range of the map's center (dependent on scale). Each scale value increases the range by 63 blocks in each direction.

For example, a map with a scale of 0 created at (0,0) will show decorations with absolute coordinates between -63.0 and 63.0. A scale-0 map created at (512,512) will show decorations between 449.0 and 575.0 (as they are within 63 blocks of the map's center). The same map at a scale of 1 will show decorations between 386.0 and 638.0 (within the 126-block range).

As maps face North, the bottom right corner is the most positive of the two coordinates.

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id must simply be a unique string, to identify the marker by.

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There's also rot, which is clockwise rotation of the symbol in degrees. There does not appear to be a limit on this; -45 is the same as 315 or 1035.

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Here's an example command, provided the map was created at (0,0) and has a scale of 0, with markers at each corner, all facing inwards:

/give @p filled_map 1 100 {Decorations:[{id:"7",type:0,x:63,z:63,rot:135},{id:"31",type:1,x:-63,z:63,rot:225},{id:"03",type:2,x:63,z:-63,rot:45},{id:"1",type:3,x:-63,z:-63,rot:-45}]}

Expanded data:

{
    Decorations:
    [
        {
            id:"7",
            type:0,
            x:63,
            z:63,
            rot:135
        },

        {
            id:"31",
            type:1,
            x:-63,
            z:63,
            rot:225
        },

        {
            id:"03",
            type:2,
            x:63,
            z:-63,
            rot:45
        },

        {
            id:"1",
            type:3,
            x:-63,
            z:-63,
            rot:-45
        }
    ]
}