I been adding some tilesets in the last few day.
This code can cut up to 1/2 of the original png file and still can be interpreted with G’MIC with base642img:
$ image.png rep_val2order , name[-2] \"Name\" serialize , e ${img2base64\ 0,0}
Which then can be interpreted back with
tile_command unserialize map.. . rm.
But, I wonder, if it is possible to compress even further.