Upload an image and choose your block palette. You will see a preview of the output map art on the right, and the original image on the left for comparison. Fiddle with the settings until you are happy with the result. Different settings work better for different images. Download the map art as a schematic that you can use with Litematica.
This tool is intended for Java edition.
On a map, if a block is higher than the block directly north of it, it gets brightened, and if it's lower, it gets darkened. This effectively triples the number of available colors compared to a flat map.
A.k.a limited staircasing. If you limit the height to just a few blocks, you get most of the benefit of staircased maps, but it will be significantly easier to build. 2 or 3 layers are often sufficient. You get diminishing increases in quality with more layers.
Layered maps are only compatible with diffusion dithering.
Only a limited range of colors can be reproduced on a map. If a color is too bright or too saturated, it will not be possible to accurately approximate it using the palette colors. The tool tries its best to do something reasonable in this case.
You may get better results if you first reduce the brightness or saturation of your image in an image editor.
Beware! Minecraft renders maps without any anti-aliasing. If you stand far enough from your map art, you will see aliasing artifacts appear. This is not really a problem for small map arts, intended to be viewed up close, but it is a problem for large map arts. Different dither methods differ in how bad the problem is and what it looks like.
Bayer - Its repeating structure will lead to very obnoxious moiré patterns. It looks as if the map art was throwing a disco party. It is completely unsuitable for large map arts.
Floyd-Steinberg, Atkinson, a dither xor, Blue noise - They produce artifacts that look like TV static. From these Atkinson is the least bad; you need to stand a little further away for the problem to occur.
a dither add - Despite having a dumb name, it's the least susceptible to aliasing problems from all the offered methods, and the one that I would recommend. There are some moiré patterns forming, but they are subtle; you need to stand really far for it to get bad.
There is a client side mod MapMipMapMod, which enables mipmapping for maps. That fixes all of these problems. Of course, you can't ensure that other players looking at your map art will have it installed.
The structure file uses the vanilla Minecraft structure format. This
format is compatible with Litematica. You can also paste the
structure into your creative world using the vanilla /place
template command. To do so you need to put the file into
the generated/minecraft/structures/ subfolder of your
Minecraft world. You may need to increase your render distance,
as the command will fail if the structure doesn't fit within your
render distance.
You need to put the map files into the data/ subfolder
of your Minecraft world. It is best to first create as many new
maps as you need in-game, and then replace their .dat
files with the generated map files.