This is a simple program that packs a Tiled tileset by removing all-black tiles, ideally you want to use this between Image2Map.py and MapWriter.py

tilesetPacker.d

/*
Tiled tileset packer
 
Copyright (c) 2014, gdm85 - https://github.com/gdm85
All rights reserved.
 
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. Neither the name of the author nor the names of its contributors may
be used to endorse or promote products derived from this software without
specific prior written permission.
 
THIS SOFTWARE IS PROVIDED BY gdm85 ''AS IS'' AND ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
IN NO EVENT SHALL gdm85 BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
OF THE POSSIBILITY OF SUCH DAMAGE.
*/

/*
	this is a simple program that packs a Tiled tileset by removing all-black tiles
	ideally you want to use this between Image2Map.py and MapWriter.py
	NOTE: expects square tiles only
*/

import std.stdio;
import dsfml.graphics;
import core.runtime;
import std.conv;

immutable int tileSz = 32;

void main()
{
	auto args = Runtime.cArgs;
	
	if (args.argc < 3) {
		writeln("Please specify input and output tilesets");
		return;
	}
	
	auto tileset = new Image();
	if(!tileset.loadFromFile(to!string(args.argv[1])))
		throw new Exception("Cannot load source tileset");
		
	// create destination tileset with maximum possible tileset size
	// it will be later trimmed down
	auto origSize = tileset.getSize();
	int origTilesCount = origSize.x * origSize.y / (tileSz * tileSz);
	auto packedTileset = new Image();
	packedTileset.create(tileSz, origTilesCount * tileSz, Color(0, 0, 0));
	
	auto newTilesCount = 0;
	
	for(int x=0;x < origSize.x;x+=tileSz){
		for(int y=0;y < origSize.y;y+=tileSz){
			// skip a fully black tile
			if (isBlackTile(tileset, x, y))
				continue;
				

			writeln("Now writing tile at " ~ to!string(x) ~ ", " ~ to!string(y));
			stdout.flush();
			
			// add tile to packed tileset
			// not using SFML copyImage because of a SEGFAULT
			//packedTileset.copyImage(tileset, 0, newTilesCount * tileSz, IntRect(x, y, tileSz, tileSz));
			copyTile(tileset, x, y, packedTileset, 0, newTilesCount * tileSz);
			newTilesCount++;
		}
	}
	
	writeln("Packed " ~ to!string(origTilesCount) ~ " tiles into " ~ to!string(newTilesCount));
	
	// create new tileset with correct height
	auto finalTileset = new Image();
	finalTileset.create(tileSz, newTilesCount * tileSz, Color(0, 0, 0));
	finalTileset.copyImage(packedTileset, 0, 0, IntRect(0,0,tileSz,newTilesCount*tileSz));
	
	finalTileset.saveToFile(to!string(args.argv[2]));
}

bool isBlackTile(Image tileset, int x, int y) {
	int w = x + tileSz;
	int h = y + tileSz;
	for(;x < w;x++){
		for(;y < h;y++){
			auto pixel = tileset.getPixel(x, y);
			
			if (pixel.r + pixel.g + pixel.b != 0)
				return false;
		}
	}	
	return true;
}

void copyTile(Image source, int srcX, int srcY, Image dest, int destX, int destY) {
	for(int x = 0;x < tileSz;x++){
		for(int y = 0;y < tileSz;y++){
			auto pixel = source.getPixel(srcX + x, srcY + y);
			
			dest.setPixel(destX + x, destY + y, pixel);
		}
	}	
}