MinecraftImageMap is a small program to convert images to minecraft maps, similar to "Image2Map". In fact, it was only made because the Linux download of that was corrupted.
The screenshots probably say more than 1000 words.
just put the .dat file inside "minecraft/saves/<Your World>/data/" as map_x.dat (x = number). Easiest way is to make a new map inside minecraft and look at its number in the items screen, then replace the dat file witrh the same number.
Inside minecraft as a map:
Inside minecraft (map inside item display case):
You'll need java version 7, but since MineCraft itself needs java, you'll probably allready have it.
If everything works, you can just double-click the jar.
Oracle pulled a fast one on us, newest (Oracle) Java versions have horrible licencing. So either choose 1.8, the last proper version, or chose OpenJDK:
Java 1.8 via Java.com
Newest Java via adoptOpenJDK.com
Would be nice if you would drop a link back to me if you put it in another forum or extend it. As for the rest, you're only bound to the licence of JNBT