LPC terrain extension
This work extends the LPC terrain tiles. Not by new terrains, but by new kinds of tiles.
The original pattern for terrain tilesets did not well support all configurations of tiles. It seems the assumption was that a single kind of terrain always comes in (possibly overlapping) rectangles of size at least 2x2. But even then, the pattern did not support the case where two such rectangles overlap at exactly one tile. The tilesets in the directory "twosided" provide the required tiles for all terrain tilesets submitted to the LPC or added since then (at the time of this writing). The tilesets also contain new tiles for the case where two rectangles touch at exactly one edge. Where feasible, the new tiles connect the two rectangles more than just two corner tiles would. But it has not always been possible. The original part of the tilesets has been unmodified, except for cement.png where the tiles at (1,1) and (2,1) were changed so that they align with the tiles at (0,2) through (2,2).
The directory "threesided" provides transitional tiles where three different terrains meet. The above tilesets implement transitions between two terrains. Observe though, that when terrain transitions consist just of one terrain being drawn on top of the other (e.g. grass over dirt or hole over whatever), threesided or even foursided transitions do not need special tiles. However, there are transitions that do not have this property (e.g. grass/water). This part of the work is incomplete.
[UPDATE (2013-1-30):] I noticed a naming mistake. The files named (anything)grassother.png should, for consistency, be named (anything)grassaltother.png instead, because the grass/other edges align with grassalt, not grass. On a related note, this update adds a further threesided transition: grassgrassaltother.png. It is Copyright 2012 by Lanea Zimmerman, modified 2013 by Mark Weyer. Furthermore, there is a new preview.
[UPDATE (2013-1-31):] As the archive had problems on some platforms, I replaced it with an uncompressed one. The contained .xcfs are now individually compressed (.pngs are always compressed anyway). The new archive also contains grassgrassaltother.png.